Consider the sentence Kim arrived or Dana left and everyone cheered. Write down the parenthesized forms to show the relative scope of and and or. Generate tree structures corresponding to both of these interpretations.
In [12]:
from nltk import CFG
sent = "Kim arrived or Dana left and everyone cheered"
sent = [word for word in sent.split()]
print sent
groucho_grammar = CFG.fromstring("""
S -> CP | VP
CP -> VP C VP | CP C VP | VP C CP
VP -> NP V
NP -> 'Kim' | 'Dana' | 'everyone'
V -> 'arrived' | 'left' |'cheered'
C -> 'or' | 'and'
""")
print groucho_grammar.productions()
parser = nltk.ChartParser(groucho_grammar)
trees = parser.parse(sent)
for tree in trees:
print tree
['Kim', 'arrived', 'or', 'Dana', 'left', 'and', 'everyone', 'cheered']
[S -> CP, S -> VP, CP -> VP C VP, CP -> CP C VP, CP -> VP C CP, VP -> NP V, NP -> 'Kim', NP -> 'Dana', NP -> 'everyone', V -> 'arrived', V -> 'left', V -> 'cheered', C -> 'or', C -> 'and']
(S
(CP
(CP (VP (NP Kim) (V arrived)) (C or) (VP (NP Dana) (V left)))
(C and)
(VP (NP everyone) (V cheered))))
(S
(CP
(VP (NP Kim) (V arrived))
(C or)
(CP
(VP (NP Dana) (V left))
(C and)
(VP (NP everyone) (V cheered)))))
The Tree class implements a variety of other useful methods. See the Tree help documentation for more details, i.e. import the Tree class and then type help(Tree).
In [31]:
from nltk import tree
str(help(tree))
---------------------------------------------------------------------------
IndexError Traceback (most recent call last)
<ipython-input-31-594c77acb95f> in <module>()
1 from nltk import tree
----> 2 str(help(tree))[1000]
IndexError: string index out of range
Help on module nltk.tree in nltk:
NAME
nltk.tree
FILE
/usr/local/lib/python2.7/dist-packages/nltk/tree.py
DESCRIPTION
Class for representing hierarchical language structures, such as
syntax trees and morphological trees.
CLASSES
__builtin__.list(__builtin__.object)
Tree
ImmutableTree
ImmutableMultiParentedTree(ImmutableTree, MultiParentedTree)
ImmutableParentedTree(ImmutableTree, ParentedTree)
ImmutableProbabilisticTree(ImmutableTree, nltk.probability.ProbabilisticMixIn)
ProbabilisticTree(Tree, nltk.probability.ProbabilisticMixIn)
__builtin__.object
nltk.probability.ProbabilisticMixIn
AbstractParentedTree(Tree)
MultiParentedTree
ParentedTree
class ImmutableMultiParentedTree(ImmutableTree, MultiParentedTree)
| Method resolution order:
| ImmutableMultiParentedTree
| ImmutableTree
| MultiParentedTree
| AbstractParentedTree
| Tree
| __builtin__.list
| __builtin__.object
|
| Methods inherited from ImmutableTree:
|
| __delitem__(self, index)
|
| __delslice__(self, i, j)
|
| __hash__(self)
|
| __iadd__(self, other)
|
| __imul__(self, other)
|
| __init__(self, node, children=None)
|
| __setitem__(self, index, value)
|
| __setslice__(self, i, j, value)
|
| append(self, v)
|
| extend(self, v)
|
| pop(self, v=None)
|
| remove(self, v)
|
| reverse(self)
|
| set_label(self, value)
| Set the node label. This will only succeed the first time the
| node label is set, which should occur in ImmutableTree.__init__().
|
| sort(self)
|
| ----------------------------------------------------------------------
| Methods inherited from MultiParentedTree:
|
| left_siblings(self)
| A list of all left siblings of this tree, in any of its parent
| trees. A tree may be its own left sibling if it is used as
| multiple contiguous children of the same parent. A tree may
| appear multiple times in this list if it is the left sibling
| of this tree with respect to multiple parents.
|
| :type: list(MultiParentedTree)
|
| parent_indices(self, parent)
| Return a list of the indices where this tree occurs as a child
| of ``parent``. If this child does not occur as a child of
| ``parent``, then the empty list is returned. The following is
| always true::
|
| for parent_index in ptree.parent_indices(parent):
| parent[parent_index] is ptree
|
| parents(self)
| The set of parents of this tree. If this tree has no parents,
| then ``parents`` is the empty set. To check if a tree is used
| as multiple children of the same parent, use the
| ``parent_indices()`` method.
|
| :type: list(MultiParentedTree)
|
| right_siblings(self)
| A list of all right siblings of this tree, in any of its parent
| trees. A tree may be its own right sibling if it is used as
| multiple contiguous children of the same parent. A tree may
| appear multiple times in this list if it is the right sibling
| of this tree with respect to multiple parents.
|
| :type: list(MultiParentedTree)
|
| roots(self)
| The set of all roots of this tree. This set is formed by
| tracing all possible parent paths until trees with no parents
| are found.
|
| :type: list(MultiParentedTree)
|
| treepositions(self, root)
| Return a list of all tree positions that can be used to reach
| this multi-parented tree starting from ``root``. I.e., the
| following is always true::
|
| for treepos in ptree.treepositions(root):
| root[treepos] is ptree
|
| ----------------------------------------------------------------------
| Methods inherited from AbstractParentedTree:
|
| __getslice__(self, start, stop)
|
| insert(self, index, child)
|
| ----------------------------------------------------------------------
| Methods inherited from Tree:
|
| __add__(self, v)
|
| __eq__(self, other)
|
| __ge__ lambda self, other
|
| __getitem__(self, index)
|
| __gt__ lambda self, other
|
| __le__ lambda self, other
|
| __lt__(self, other)
|
| __mul__(self, v)
|
| __ne__ lambda self, other
| # @total_ordering doesn't work here, since the class inherits from a builtin class
|
| __radd__(self, v)
|
| __repr__(self)
|
| __rmul__(self, v)
|
| __str__(self)
|
| __unicode__ = __str__(self)
|
| chomsky_normal_form(self, factor=u'right', horzMarkov=None, vertMarkov=0, childChar=u'|', parentChar=u'^')
| This method can modify a tree in three ways:
|
| 1. Convert a tree into its Chomsky Normal Form (CNF)
| equivalent -- Every subtree has either two non-terminals
| or one terminal as its children. This process requires
| the creation of more"artificial" non-terminal nodes.
| 2. Markov (vertical) smoothing of children in new artificial
| nodes
| 3. Horizontal (parent) annotation of nodes
|
| :param factor: Right or left factoring method (default = "right")
| :type factor: str = [left|right]
| :param horzMarkov: Markov order for sibling smoothing in artificial nodes (None (default) = include all siblings)
| :type horzMarkov: int | None
| :param vertMarkov: Markov order for parent smoothing (0 (default) = no vertical annotation)
| :type vertMarkov: int | None
| :param childChar: A string used in construction of the artificial nodes, separating the head of the
| original subtree from the child nodes that have yet to be expanded (default = "|")
| :type childChar: str
| :param parentChar: A string used to separate the node representation from its vertical annotation
| :type parentChar: str
|
| collapse_unary(self, collapsePOS=False, collapseRoot=False, joinChar=u'+')
| Collapse subtrees with a single child (ie. unary productions)
| into a new non-terminal (Tree node) joined by 'joinChar'.
| This is useful when working with algorithms that do not allow
| unary productions, and completely removing the unary productions
| would require loss of useful information. The Tree is modified
| directly (since it is passed by reference) and no value is returned.
|
| :param collapsePOS: 'False' (default) will not collapse the parent of leaf nodes (ie.
| Part-of-Speech tags) since they are always unary productions
| :type collapsePOS: bool
| :param collapseRoot: 'False' (default) will not modify the root production
| if it is unary. For the Penn WSJ treebank corpus, this corresponds
| to the TOP -> productions.
| :type collapseRoot: bool
| :param joinChar: A string used to connect collapsed node values (default = "+")
| :type joinChar: str
|
| copy(self, deep=False)
|
| draw(self)
| Open a new window containing a graphical diagram of this tree.
|
| flatten(self)
| Return a flat version of the tree, with all non-root non-terminals removed.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> print(t.flatten())
| (S the dog chased the cat)
|
| :return: a tree consisting of this tree's root connected directly to
| its leaves, omitting all intervening non-terminal nodes.
| :rtype: Tree
|
| freeze(self, leaf_freezer=None)
|
| height(self)
| Return the height of the tree.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> t.height()
| 5
| >>> print(t[0,0])
| (D the)
| >>> t[0,0].height()
| 2
|
| :return: The height of this tree. The height of a tree
| containing no children is 1; the height of a tree
| containing only leaves is 2; and the height of any other
| tree is one plus the maximum of its children's
| heights.
| :rtype: int
|
| label(self)
| Return the node label of the tree.
|
| >>> t = Tree.fromstring('(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))')
| >>> t.label()
| 'S'
|
| :return: the node label (typically a string)
| :rtype: any
|
| leaf_treeposition(self, index)
| :return: The tree position of the ``index``-th leaf in this
| tree. I.e., if ``tp=self.leaf_treeposition(i)``, then
| ``self[tp]==self.leaves()[i]``.
|
| :raise IndexError: If this tree contains fewer than ``index+1``
| leaves, or if ``index<0``.
|
| leaves(self)
| Return the leaves of the tree.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> t.leaves()
| ['the', 'dog', 'chased', 'the', 'cat']
|
| :return: a list containing this tree's leaves.
| The order reflects the order of the
| leaves in the tree's hierarchical structure.
| :rtype: list
|
| pformat(self, margin=70, indent=0, nodesep=u'', parens=u'()', quotes=False)
| :return: A pretty-printed string representation of this tree.
| :rtype: str
| :param margin: The right margin at which to do line-wrapping.
| :type margin: int
| :param indent: The indentation level at which printing
| begins. This number is used to decide how far to indent
| subsequent lines.
| :type indent: int
| :param nodesep: A string that is used to separate the node
| from the children. E.g., the default value ``':'`` gives
| trees like ``(S: (NP: I) (VP: (V: saw) (NP: it)))``.
|
| pformat_latex_qtree(self)
| Returns a representation of the tree compatible with the
| LaTeX qtree package. This consists of the string ``\Tree``
| followed by the tree represented in bracketed notation.
|
| For example, the following result was generated from a parse tree of
| the sentence ``The announcement astounded us``::
|
| \Tree [.I'' [.N'' [.D The ] [.N' [.N announcement ] ] ]
| [.I' [.V'' [.V' [.V astounded ] [.N'' [.N' [.N us ] ] ] ] ] ] ]
|
| See http://www.ling.upenn.edu/advice/latex.html for the LaTeX
| style file for the qtree package.
|
| :return: A latex qtree representation of this tree.
| :rtype: str
|
| pos(self)
| Return a sequence of pos-tagged words extracted from the tree.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> t.pos()
| [('the', 'D'), ('dog', 'N'), ('chased', 'V'), ('the', 'D'), ('cat', 'N')]
|
| :return: a list of tuples containing leaves and pre-terminals (part-of-speech tags).
| The order reflects the order of the leaves in the tree's hierarchical structure.
| :rtype: list(tuple)
|
| pprint(self, **kwargs)
| Print a string representation of this Tree to 'stream'
|
| pretty_print(self, sentence=None, highlight=(), stream=None, **kwargs)
| Pretty-print this tree as ASCII or Unicode art.
| For explanation of the arguments, see the documentation for
| `nltk.treeprettyprinter.TreePrettyPrinter`.
|
| productions(self)
| Generate the productions that correspond to the non-terminal nodes of the tree.
| For each subtree of the form (P: C1 C2 ... Cn) this produces a production of the
| form P -> C1 C2 ... Cn.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> t.productions()
| [S -> NP VP, NP -> D N, D -> 'the', N -> 'dog', VP -> V NP, V -> 'chased',
| NP -> D N, D -> 'the', N -> 'cat']
|
| :rtype: list(Production)
|
| subtrees(self, filter=None)
| Generate all the subtrees of this tree, optionally restricted
| to trees matching the filter function.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> for s in t.subtrees(lambda t: t.height() == 2):
| ... print(s)
| (D the)
| (N dog)
| (V chased)
| (D the)
| (N cat)
|
| :type filter: function
| :param filter: the function to filter all local trees
|
| treeposition_spanning_leaves(self, start, end)
| :return: The tree position of the lowest descendant of this
| tree that dominates ``self.leaves()[start:end]``.
| :raise ValueError: if ``end <= start``
|
| un_chomsky_normal_form(self, expandUnary=True, childChar=u'|', parentChar=u'^', unaryChar=u'+')
| This method modifies the tree in three ways:
|
| 1. Transforms a tree in Chomsky Normal Form back to its
| original structure (branching greater than two)
| 2. Removes any parent annotation (if it exists)
| 3. (optional) expands unary subtrees (if previously
| collapsed with collapseUnary(...) )
|
| :param expandUnary: Flag to expand unary or not (default = True)
| :type expandUnary: bool
| :param childChar: A string separating the head node from its children in an artificial node (default = "|")
| :type childChar: str
| :param parentChar: A sting separating the node label from its parent annotation (default = "^")
| :type parentChar: str
| :param unaryChar: A string joining two non-terminals in a unary production (default = "+")
| :type unaryChar: str
|
| unicode_repr = __repr__(self)
|
| ----------------------------------------------------------------------
| Class methods inherited from Tree:
|
| convert(cls, tree) from __builtin__.type
| Convert a tree between different subtypes of Tree. ``cls`` determines
| which class will be used to encode the new tree.
|
| :type tree: Tree
| :param tree: The tree that should be converted.
| :return: The new Tree.
|
| fromstring(cls, s, brackets=u'()', read_node=None, read_leaf=None, node_pattern=None, leaf_pattern=None, remove_empty_top_bracketing=False) from __builtin__.type
| Read a bracketed tree string and return the resulting tree.
| Trees are represented as nested brackettings, such as::
|
| (S (NP (NNP John)) (VP (V runs)))
|
| :type s: str
| :param s: The string to read
|
| :type brackets: str (length=2)
| :param brackets: The bracket characters used to mark the
| beginning and end of trees and subtrees.
|
| :type read_node: function
| :type read_leaf: function
| :param read_node, read_leaf: If specified, these functions
| are applied to the substrings of ``s`` corresponding to
| nodes and leaves (respectively) to obtain the values for
| those nodes and leaves. They should have the following
| signature:
|
| read_node(str) -> value
|
| For example, these functions could be used to process nodes
| and leaves whose values should be some type other than
| string (such as ``FeatStruct``).
| Note that by default, node strings and leaf strings are
| delimited by whitespace and brackets; to override this
| default, use the ``node_pattern`` and ``leaf_pattern``
| arguments.
|
| :type node_pattern: str
| :type leaf_pattern: str
| :param node_pattern, leaf_pattern: Regular expression patterns
| used to find node and leaf substrings in ``s``. By
| default, both nodes patterns are defined to match any
| sequence of non-whitespace non-bracket characters.
|
| :type remove_empty_top_bracketing: bool
| :param remove_empty_top_bracketing: If the resulting tree has
| an empty node label, and is length one, then return its
| single child instead. This is useful for treebank trees,
| which sometimes contain an extra level of bracketing.
|
| :return: A tree corresponding to the string representation ``s``.
| If this class method is called using a subclass of Tree,
| then it will return a tree of that type.
| :rtype: Tree
|
| ----------------------------------------------------------------------
| Data descriptors inherited from Tree:
|
| __dict__
| dictionary for instance variables (if defined)
|
| __weakref__
| list of weak references to the object (if defined)
|
| node
| Outdated method to access the node value; use the label() method instead.
|
| ----------------------------------------------------------------------
| Methods inherited from __builtin__.list:
|
| __contains__(...)
| x.__contains__(y) <==> y in x
|
| __getattribute__(...)
| x.__getattribute__('name') <==> x.name
|
| __iter__(...)
| x.__iter__() <==> iter(x)
|
| __len__(...)
| x.__len__() <==> len(x)
|
| __reversed__(...)
| L.__reversed__() -- return a reverse iterator over the list
|
| __sizeof__(...)
| L.__sizeof__() -- size of L in memory, in bytes
|
| count(...)
| L.count(value) -> integer -- return number of occurrences of value
|
| index(...)
| L.index(value, [start, [stop]]) -> integer -- return first index of value.
| Raises ValueError if the value is not present.
|
| ----------------------------------------------------------------------
| Data and other attributes inherited from __builtin__.list:
|
| __new__ = <built-in method __new__ of type object>
| T.__new__(S, ...) -> a new object with type S, a subtype of T
class ImmutableParentedTree(ImmutableTree, ParentedTree)
| Method resolution order:
| ImmutableParentedTree
| ImmutableTree
| ParentedTree
| AbstractParentedTree
| Tree
| __builtin__.list
| __builtin__.object
|
| Methods inherited from ImmutableTree:
|
| __delitem__(self, index)
|
| __delslice__(self, i, j)
|
| __hash__(self)
|
| __iadd__(self, other)
|
| __imul__(self, other)
|
| __init__(self, node, children=None)
|
| __setitem__(self, index, value)
|
| __setslice__(self, i, j, value)
|
| append(self, v)
|
| extend(self, v)
|
| pop(self, v=None)
|
| remove(self, v)
|
| reverse(self)
|
| set_label(self, value)
| Set the node label. This will only succeed the first time the
| node label is set, which should occur in ImmutableTree.__init__().
|
| sort(self)
|
| ----------------------------------------------------------------------
| Methods inherited from ParentedTree:
|
| left_sibling(self)
| The left sibling of this tree, or None if it has none.
|
| parent(self)
| The parent of this tree, or None if it has no parent.
|
| parent_index(self)
| The index of this tree in its parent. I.e.,
| ``ptree.parent()[ptree.parent_index()] is ptree``. Note that
| ``ptree.parent_index()`` is not necessarily equal to
| ``ptree.parent.index(ptree)``, since the ``index()`` method
| returns the first child that is equal to its argument.
|
| right_sibling(self)
| The right sibling of this tree, or None if it has none.
|
| root(self)
| The root of this tree. I.e., the unique ancestor of this tree
| whose parent is None. If ``ptree.parent()`` is None, then
| ``ptree`` is its own root.
|
| treeposition(self)
| The tree position of this tree, relative to the root of the
| tree. I.e., ``ptree.root[ptree.treeposition] is ptree``.
|
| ----------------------------------------------------------------------
| Methods inherited from AbstractParentedTree:
|
| __getslice__(self, start, stop)
|
| insert(self, index, child)
|
| ----------------------------------------------------------------------
| Methods inherited from Tree:
|
| __add__(self, v)
|
| __eq__(self, other)
|
| __ge__ lambda self, other
|
| __getitem__(self, index)
|
| __gt__ lambda self, other
|
| __le__ lambda self, other
|
| __lt__(self, other)
|
| __mul__(self, v)
|
| __ne__ lambda self, other
| # @total_ordering doesn't work here, since the class inherits from a builtin class
|
| __radd__(self, v)
|
| __repr__(self)
|
| __rmul__(self, v)
|
| __str__(self)
|
| __unicode__ = __str__(self)
|
| chomsky_normal_form(self, factor=u'right', horzMarkov=None, vertMarkov=0, childChar=u'|', parentChar=u'^')
| This method can modify a tree in three ways:
|
| 1. Convert a tree into its Chomsky Normal Form (CNF)
| equivalent -- Every subtree has either two non-terminals
| or one terminal as its children. This process requires
| the creation of more"artificial" non-terminal nodes.
| 2. Markov (vertical) smoothing of children in new artificial
| nodes
| 3. Horizontal (parent) annotation of nodes
|
| :param factor: Right or left factoring method (default = "right")
| :type factor: str = [left|right]
| :param horzMarkov: Markov order for sibling smoothing in artificial nodes (None (default) = include all siblings)
| :type horzMarkov: int | None
| :param vertMarkov: Markov order for parent smoothing (0 (default) = no vertical annotation)
| :type vertMarkov: int | None
| :param childChar: A string used in construction of the artificial nodes, separating the head of the
| original subtree from the child nodes that have yet to be expanded (default = "|")
| :type childChar: str
| :param parentChar: A string used to separate the node representation from its vertical annotation
| :type parentChar: str
|
| collapse_unary(self, collapsePOS=False, collapseRoot=False, joinChar=u'+')
| Collapse subtrees with a single child (ie. unary productions)
| into a new non-terminal (Tree node) joined by 'joinChar'.
| This is useful when working with algorithms that do not allow
| unary productions, and completely removing the unary productions
| would require loss of useful information. The Tree is modified
| directly (since it is passed by reference) and no value is returned.
|
| :param collapsePOS: 'False' (default) will not collapse the parent of leaf nodes (ie.
| Part-of-Speech tags) since they are always unary productions
| :type collapsePOS: bool
| :param collapseRoot: 'False' (default) will not modify the root production
| if it is unary. For the Penn WSJ treebank corpus, this corresponds
| to the TOP -> productions.
| :type collapseRoot: bool
| :param joinChar: A string used to connect collapsed node values (default = "+")
| :type joinChar: str
|
| copy(self, deep=False)
|
| draw(self)
| Open a new window containing a graphical diagram of this tree.
|
| flatten(self)
| Return a flat version of the tree, with all non-root non-terminals removed.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> print(t.flatten())
| (S the dog chased the cat)
|
| :return: a tree consisting of this tree's root connected directly to
| its leaves, omitting all intervening non-terminal nodes.
| :rtype: Tree
|
| freeze(self, leaf_freezer=None)
|
| height(self)
| Return the height of the tree.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> t.height()
| 5
| >>> print(t[0,0])
| (D the)
| >>> t[0,0].height()
| 2
|
| :return: The height of this tree. The height of a tree
| containing no children is 1; the height of a tree
| containing only leaves is 2; and the height of any other
| tree is one plus the maximum of its children's
| heights.
| :rtype: int
|
| label(self)
| Return the node label of the tree.
|
| >>> t = Tree.fromstring('(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))')
| >>> t.label()
| 'S'
|
| :return: the node label (typically a string)
| :rtype: any
|
| leaf_treeposition(self, index)
| :return: The tree position of the ``index``-th leaf in this
| tree. I.e., if ``tp=self.leaf_treeposition(i)``, then
| ``self[tp]==self.leaves()[i]``.
|
| :raise IndexError: If this tree contains fewer than ``index+1``
| leaves, or if ``index<0``.
|
| leaves(self)
| Return the leaves of the tree.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> t.leaves()
| ['the', 'dog', 'chased', 'the', 'cat']
|
| :return: a list containing this tree's leaves.
| The order reflects the order of the
| leaves in the tree's hierarchical structure.
| :rtype: list
|
| pformat(self, margin=70, indent=0, nodesep=u'', parens=u'()', quotes=False)
| :return: A pretty-printed string representation of this tree.
| :rtype: str
| :param margin: The right margin at which to do line-wrapping.
| :type margin: int
| :param indent: The indentation level at which printing
| begins. This number is used to decide how far to indent
| subsequent lines.
| :type indent: int
| :param nodesep: A string that is used to separate the node
| from the children. E.g., the default value ``':'`` gives
| trees like ``(S: (NP: I) (VP: (V: saw) (NP: it)))``.
|
| pformat_latex_qtree(self)
| Returns a representation of the tree compatible with the
| LaTeX qtree package. This consists of the string ``\Tree``
| followed by the tree represented in bracketed notation.
|
| For example, the following result was generated from a parse tree of
| the sentence ``The announcement astounded us``::
|
| \Tree [.I'' [.N'' [.D The ] [.N' [.N announcement ] ] ]
| [.I' [.V'' [.V' [.V astounded ] [.N'' [.N' [.N us ] ] ] ] ] ] ]
|
| See http://www.ling.upenn.edu/advice/latex.html for the LaTeX
| style file for the qtree package.
|
| :return: A latex qtree representation of this tree.
| :rtype: str
|
| pos(self)
| Return a sequence of pos-tagged words extracted from the tree.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> t.pos()
| [('the', 'D'), ('dog', 'N'), ('chased', 'V'), ('the', 'D'), ('cat', 'N')]
|
| :return: a list of tuples containing leaves and pre-terminals (part-of-speech tags).
| The order reflects the order of the leaves in the tree's hierarchical structure.
| :rtype: list(tuple)
|
| pprint(self, **kwargs)
| Print a string representation of this Tree to 'stream'
|
| pretty_print(self, sentence=None, highlight=(), stream=None, **kwargs)
| Pretty-print this tree as ASCII or Unicode art.
| For explanation of the arguments, see the documentation for
| `nltk.treeprettyprinter.TreePrettyPrinter`.
|
| productions(self)
| Generate the productions that correspond to the non-terminal nodes of the tree.
| For each subtree of the form (P: C1 C2 ... Cn) this produces a production of the
| form P -> C1 C2 ... Cn.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> t.productions()
| [S -> NP VP, NP -> D N, D -> 'the', N -> 'dog', VP -> V NP, V -> 'chased',
| NP -> D N, D -> 'the', N -> 'cat']
|
| :rtype: list(Production)
|
| subtrees(self, filter=None)
| Generate all the subtrees of this tree, optionally restricted
| to trees matching the filter function.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> for s in t.subtrees(lambda t: t.height() == 2):
| ... print(s)
| (D the)
| (N dog)
| (V chased)
| (D the)
| (N cat)
|
| :type filter: function
| :param filter: the function to filter all local trees
|
| treeposition_spanning_leaves(self, start, end)
| :return: The tree position of the lowest descendant of this
| tree that dominates ``self.leaves()[start:end]``.
| :raise ValueError: if ``end <= start``
|
| treepositions(self, order=u'preorder')
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> t.treepositions() # doctest: +ELLIPSIS
| [(), (0,), (0, 0), (0, 0, 0), (0, 1), (0, 1, 0), (1,), (1, 0), (1, 0, 0), ...]
| >>> for pos in t.treepositions('leaves'):
| ... t[pos] = t[pos][::-1].upper()
| >>> print(t)
| (S (NP (D EHT) (N GOD)) (VP (V DESAHC) (NP (D EHT) (N TAC))))
|
| :param order: One of: ``preorder``, ``postorder``, ``bothorder``,
| ``leaves``.
|
| un_chomsky_normal_form(self, expandUnary=True, childChar=u'|', parentChar=u'^', unaryChar=u'+')
| This method modifies the tree in three ways:
|
| 1. Transforms a tree in Chomsky Normal Form back to its
| original structure (branching greater than two)
| 2. Removes any parent annotation (if it exists)
| 3. (optional) expands unary subtrees (if previously
| collapsed with collapseUnary(...) )
|
| :param expandUnary: Flag to expand unary or not (default = True)
| :type expandUnary: bool
| :param childChar: A string separating the head node from its children in an artificial node (default = "|")
| :type childChar: str
| :param parentChar: A sting separating the node label from its parent annotation (default = "^")
| :type parentChar: str
| :param unaryChar: A string joining two non-terminals in a unary production (default = "+")
| :type unaryChar: str
|
| unicode_repr = __repr__(self)
|
| ----------------------------------------------------------------------
| Class methods inherited from Tree:
|
| convert(cls, tree) from __builtin__.type
| Convert a tree between different subtypes of Tree. ``cls`` determines
| which class will be used to encode the new tree.
|
| :type tree: Tree
| :param tree: The tree that should be converted.
| :return: The new Tree.
|
| fromstring(cls, s, brackets=u'()', read_node=None, read_leaf=None, node_pattern=None, leaf_pattern=None, remove_empty_top_bracketing=False) from __builtin__.type
| Read a bracketed tree string and return the resulting tree.
| Trees are represented as nested brackettings, such as::
|
| (S (NP (NNP John)) (VP (V runs)))
|
| :type s: str
| :param s: The string to read
|
| :type brackets: str (length=2)
| :param brackets: The bracket characters used to mark the
| beginning and end of trees and subtrees.
|
| :type read_node: function
| :type read_leaf: function
| :param read_node, read_leaf: If specified, these functions
| are applied to the substrings of ``s`` corresponding to
| nodes and leaves (respectively) to obtain the values for
| those nodes and leaves. They should have the following
| signature:
|
| read_node(str) -> value
|
| For example, these functions could be used to process nodes
| and leaves whose values should be some type other than
| string (such as ``FeatStruct``).
| Note that by default, node strings and leaf strings are
| delimited by whitespace and brackets; to override this
| default, use the ``node_pattern`` and ``leaf_pattern``
| arguments.
|
| :type node_pattern: str
| :type leaf_pattern: str
| :param node_pattern, leaf_pattern: Regular expression patterns
| used to find node and leaf substrings in ``s``. By
| default, both nodes patterns are defined to match any
| sequence of non-whitespace non-bracket characters.
|
| :type remove_empty_top_bracketing: bool
| :param remove_empty_top_bracketing: If the resulting tree has
| an empty node label, and is length one, then return its
| single child instead. This is useful for treebank trees,
| which sometimes contain an extra level of bracketing.
|
| :return: A tree corresponding to the string representation ``s``.
| If this class method is called using a subclass of Tree,
| then it will return a tree of that type.
| :rtype: Tree
|
| ----------------------------------------------------------------------
| Data descriptors inherited from Tree:
|
| __dict__
| dictionary for instance variables (if defined)
|
| __weakref__
| list of weak references to the object (if defined)
|
| node
| Outdated method to access the node value; use the label() method instead.
|
| ----------------------------------------------------------------------
| Methods inherited from __builtin__.list:
|
| __contains__(...)
| x.__contains__(y) <==> y in x
|
| __getattribute__(...)
| x.__getattribute__('name') <==> x.name
|
| __iter__(...)
| x.__iter__() <==> iter(x)
|
| __len__(...)
| x.__len__() <==> len(x)
|
| __reversed__(...)
| L.__reversed__() -- return a reverse iterator over the list
|
| __sizeof__(...)
| L.__sizeof__() -- size of L in memory, in bytes
|
| count(...)
| L.count(value) -> integer -- return number of occurrences of value
|
| index(...)
| L.index(value, [start, [stop]]) -> integer -- return first index of value.
| Raises ValueError if the value is not present.
|
| ----------------------------------------------------------------------
| Data and other attributes inherited from __builtin__.list:
|
| __new__ = <built-in method __new__ of type object>
| T.__new__(S, ...) -> a new object with type S, a subtype of T
class ImmutableProbabilisticTree(ImmutableTree, nltk.probability.ProbabilisticMixIn)
| Method resolution order:
| ImmutableProbabilisticTree
| ImmutableTree
| Tree
| __builtin__.list
| nltk.probability.ProbabilisticMixIn
| __builtin__.object
|
| Methods defined here:
|
| __init__(self, node, children=None, **prob_kwargs)
|
| __repr__(self)
|
| __str__(self)
|
| __unicode__ = __str__(self)
|
| copy(self, deep=False)
|
| unicode_repr = __repr__(self)
|
| ----------------------------------------------------------------------
| Class methods defined here:
|
| convert(cls, val) from __builtin__.type
|
| ----------------------------------------------------------------------
| Methods inherited from ImmutableTree:
|
| __delitem__(self, index)
|
| __delslice__(self, i, j)
|
| __hash__(self)
|
| __iadd__(self, other)
|
| __imul__(self, other)
|
| __setitem__(self, index, value)
|
| __setslice__(self, i, j, value)
|
| append(self, v)
|
| extend(self, v)
|
| pop(self, v=None)
|
| remove(self, v)
|
| reverse(self)
|
| set_label(self, value)
| Set the node label. This will only succeed the first time the
| node label is set, which should occur in ImmutableTree.__init__().
|
| sort(self)
|
| ----------------------------------------------------------------------
| Methods inherited from Tree:
|
| __add__(self, v)
|
| __eq__(self, other)
|
| __ge__ lambda self, other
|
| __getitem__(self, index)
|
| __gt__ lambda self, other
|
| __le__ lambda self, other
|
| __lt__(self, other)
|
| __mul__(self, v)
|
| __ne__ lambda self, other
| # @total_ordering doesn't work here, since the class inherits from a builtin class
|
| __radd__(self, v)
|
| __rmul__(self, v)
|
| chomsky_normal_form(self, factor=u'right', horzMarkov=None, vertMarkov=0, childChar=u'|', parentChar=u'^')
| This method can modify a tree in three ways:
|
| 1. Convert a tree into its Chomsky Normal Form (CNF)
| equivalent -- Every subtree has either two non-terminals
| or one terminal as its children. This process requires
| the creation of more"artificial" non-terminal nodes.
| 2. Markov (vertical) smoothing of children in new artificial
| nodes
| 3. Horizontal (parent) annotation of nodes
|
| :param factor: Right or left factoring method (default = "right")
| :type factor: str = [left|right]
| :param horzMarkov: Markov order for sibling smoothing in artificial nodes (None (default) = include all siblings)
| :type horzMarkov: int | None
| :param vertMarkov: Markov order for parent smoothing (0 (default) = no vertical annotation)
| :type vertMarkov: int | None
| :param childChar: A string used in construction of the artificial nodes, separating the head of the
| original subtree from the child nodes that have yet to be expanded (default = "|")
| :type childChar: str
| :param parentChar: A string used to separate the node representation from its vertical annotation
| :type parentChar: str
|
| collapse_unary(self, collapsePOS=False, collapseRoot=False, joinChar=u'+')
| Collapse subtrees with a single child (ie. unary productions)
| into a new non-terminal (Tree node) joined by 'joinChar'.
| This is useful when working with algorithms that do not allow
| unary productions, and completely removing the unary productions
| would require loss of useful information. The Tree is modified
| directly (since it is passed by reference) and no value is returned.
|
| :param collapsePOS: 'False' (default) will not collapse the parent of leaf nodes (ie.
| Part-of-Speech tags) since they are always unary productions
| :type collapsePOS: bool
| :param collapseRoot: 'False' (default) will not modify the root production
| if it is unary. For the Penn WSJ treebank corpus, this corresponds
| to the TOP -> productions.
| :type collapseRoot: bool
| :param joinChar: A string used to connect collapsed node values (default = "+")
| :type joinChar: str
|
| draw(self)
| Open a new window containing a graphical diagram of this tree.
|
| flatten(self)
| Return a flat version of the tree, with all non-root non-terminals removed.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> print(t.flatten())
| (S the dog chased the cat)
|
| :return: a tree consisting of this tree's root connected directly to
| its leaves, omitting all intervening non-terminal nodes.
| :rtype: Tree
|
| freeze(self, leaf_freezer=None)
|
| height(self)
| Return the height of the tree.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> t.height()
| 5
| >>> print(t[0,0])
| (D the)
| >>> t[0,0].height()
| 2
|
| :return: The height of this tree. The height of a tree
| containing no children is 1; the height of a tree
| containing only leaves is 2; and the height of any other
| tree is one plus the maximum of its children's
| heights.
| :rtype: int
|
| label(self)
| Return the node label of the tree.
|
| >>> t = Tree.fromstring('(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))')
| >>> t.label()
| 'S'
|
| :return: the node label (typically a string)
| :rtype: any
|
| leaf_treeposition(self, index)
| :return: The tree position of the ``index``-th leaf in this
| tree. I.e., if ``tp=self.leaf_treeposition(i)``, then
| ``self[tp]==self.leaves()[i]``.
|
| :raise IndexError: If this tree contains fewer than ``index+1``
| leaves, or if ``index<0``.
|
| leaves(self)
| Return the leaves of the tree.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> t.leaves()
| ['the', 'dog', 'chased', 'the', 'cat']
|
| :return: a list containing this tree's leaves.
| The order reflects the order of the
| leaves in the tree's hierarchical structure.
| :rtype: list
|
| pformat(self, margin=70, indent=0, nodesep=u'', parens=u'()', quotes=False)
| :return: A pretty-printed string representation of this tree.
| :rtype: str
| :param margin: The right margin at which to do line-wrapping.
| :type margin: int
| :param indent: The indentation level at which printing
| begins. This number is used to decide how far to indent
| subsequent lines.
| :type indent: int
| :param nodesep: A string that is used to separate the node
| from the children. E.g., the default value ``':'`` gives
| trees like ``(S: (NP: I) (VP: (V: saw) (NP: it)))``.
|
| pformat_latex_qtree(self)
| Returns a representation of the tree compatible with the
| LaTeX qtree package. This consists of the string ``\Tree``
| followed by the tree represented in bracketed notation.
|
| For example, the following result was generated from a parse tree of
| the sentence ``The announcement astounded us``::
|
| \Tree [.I'' [.N'' [.D The ] [.N' [.N announcement ] ] ]
| [.I' [.V'' [.V' [.V astounded ] [.N'' [.N' [.N us ] ] ] ] ] ] ]
|
| See http://www.ling.upenn.edu/advice/latex.html for the LaTeX
| style file for the qtree package.
|
| :return: A latex qtree representation of this tree.
| :rtype: str
|
| pos(self)
| Return a sequence of pos-tagged words extracted from the tree.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> t.pos()
| [('the', 'D'), ('dog', 'N'), ('chased', 'V'), ('the', 'D'), ('cat', 'N')]
|
| :return: a list of tuples containing leaves and pre-terminals (part-of-speech tags).
| The order reflects the order of the leaves in the tree's hierarchical structure.
| :rtype: list(tuple)
|
| pprint(self, **kwargs)
| Print a string representation of this Tree to 'stream'
|
| pretty_print(self, sentence=None, highlight=(), stream=None, **kwargs)
| Pretty-print this tree as ASCII or Unicode art.
| For explanation of the arguments, see the documentation for
| `nltk.treeprettyprinter.TreePrettyPrinter`.
|
| productions(self)
| Generate the productions that correspond to the non-terminal nodes of the tree.
| For each subtree of the form (P: C1 C2 ... Cn) this produces a production of the
| form P -> C1 C2 ... Cn.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> t.productions()
| [S -> NP VP, NP -> D N, D -> 'the', N -> 'dog', VP -> V NP, V -> 'chased',
| NP -> D N, D -> 'the', N -> 'cat']
|
| :rtype: list(Production)
|
| subtrees(self, filter=None)
| Generate all the subtrees of this tree, optionally restricted
| to trees matching the filter function.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> for s in t.subtrees(lambda t: t.height() == 2):
| ... print(s)
| (D the)
| (N dog)
| (V chased)
| (D the)
| (N cat)
|
| :type filter: function
| :param filter: the function to filter all local trees
|
| treeposition_spanning_leaves(self, start, end)
| :return: The tree position of the lowest descendant of this
| tree that dominates ``self.leaves()[start:end]``.
| :raise ValueError: if ``end <= start``
|
| treepositions(self, order=u'preorder')
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> t.treepositions() # doctest: +ELLIPSIS
| [(), (0,), (0, 0), (0, 0, 0), (0, 1), (0, 1, 0), (1,), (1, 0), (1, 0, 0), ...]
| >>> for pos in t.treepositions('leaves'):
| ... t[pos] = t[pos][::-1].upper()
| >>> print(t)
| (S (NP (D EHT) (N GOD)) (VP (V DESAHC) (NP (D EHT) (N TAC))))
|
| :param order: One of: ``preorder``, ``postorder``, ``bothorder``,
| ``leaves``.
|
| un_chomsky_normal_form(self, expandUnary=True, childChar=u'|', parentChar=u'^', unaryChar=u'+')
| This method modifies the tree in three ways:
|
| 1. Transforms a tree in Chomsky Normal Form back to its
| original structure (branching greater than two)
| 2. Removes any parent annotation (if it exists)
| 3. (optional) expands unary subtrees (if previously
| collapsed with collapseUnary(...) )
|
| :param expandUnary: Flag to expand unary or not (default = True)
| :type expandUnary: bool
| :param childChar: A string separating the head node from its children in an artificial node (default = "|")
| :type childChar: str
| :param parentChar: A sting separating the node label from its parent annotation (default = "^")
| :type parentChar: str
| :param unaryChar: A string joining two non-terminals in a unary production (default = "+")
| :type unaryChar: str
|
| ----------------------------------------------------------------------
| Class methods inherited from Tree:
|
| fromstring(cls, s, brackets=u'()', read_node=None, read_leaf=None, node_pattern=None, leaf_pattern=None, remove_empty_top_bracketing=False) from __builtin__.type
| Read a bracketed tree string and return the resulting tree.
| Trees are represented as nested brackettings, such as::
|
| (S (NP (NNP John)) (VP (V runs)))
|
| :type s: str
| :param s: The string to read
|
| :type brackets: str (length=2)
| :param brackets: The bracket characters used to mark the
| beginning and end of trees and subtrees.
|
| :type read_node: function
| :type read_leaf: function
| :param read_node, read_leaf: If specified, these functions
| are applied to the substrings of ``s`` corresponding to
| nodes and leaves (respectively) to obtain the values for
| those nodes and leaves. They should have the following
| signature:
|
| read_node(str) -> value
|
| For example, these functions could be used to process nodes
| and leaves whose values should be some type other than
| string (such as ``FeatStruct``).
| Note that by default, node strings and leaf strings are
| delimited by whitespace and brackets; to override this
| default, use the ``node_pattern`` and ``leaf_pattern``
| arguments.
|
| :type node_pattern: str
| :type leaf_pattern: str
| :param node_pattern, leaf_pattern: Regular expression patterns
| used to find node and leaf substrings in ``s``. By
| default, both nodes patterns are defined to match any
| sequence of non-whitespace non-bracket characters.
|
| :type remove_empty_top_bracketing: bool
| :param remove_empty_top_bracketing: If the resulting tree has
| an empty node label, and is length one, then return its
| single child instead. This is useful for treebank trees,
| which sometimes contain an extra level of bracketing.
|
| :return: A tree corresponding to the string representation ``s``.
| If this class method is called using a subclass of Tree,
| then it will return a tree of that type.
| :rtype: Tree
|
| ----------------------------------------------------------------------
| Data descriptors inherited from Tree:
|
| __dict__
| dictionary for instance variables (if defined)
|
| __weakref__
| list of weak references to the object (if defined)
|
| node
| Outdated method to access the node value; use the label() method instead.
|
| ----------------------------------------------------------------------
| Methods inherited from __builtin__.list:
|
| __contains__(...)
| x.__contains__(y) <==> y in x
|
| __getattribute__(...)
| x.__getattribute__('name') <==> x.name
|
| __getslice__(...)
| x.__getslice__(i, j) <==> x[i:j]
|
| Use of negative indices is not supported.
|
| __iter__(...)
| x.__iter__() <==> iter(x)
|
| __len__(...)
| x.__len__() <==> len(x)
|
| __reversed__(...)
| L.__reversed__() -- return a reverse iterator over the list
|
| __sizeof__(...)
| L.__sizeof__() -- size of L in memory, in bytes
|
| count(...)
| L.count(value) -> integer -- return number of occurrences of value
|
| index(...)
| L.index(value, [start, [stop]]) -> integer -- return first index of value.
| Raises ValueError if the value is not present.
|
| insert(...)
| L.insert(index, object) -- insert object before index
|
| ----------------------------------------------------------------------
| Data and other attributes inherited from __builtin__.list:
|
| __new__ = <built-in method __new__ of type object>
| T.__new__(S, ...) -> a new object with type S, a subtype of T
|
| ----------------------------------------------------------------------
| Methods inherited from nltk.probability.ProbabilisticMixIn:
|
| logprob(self)
| Return ``log(p)``, where ``p`` is the probability associated
| with this object.
|
| :rtype: float
|
| prob(self)
| Return the probability associated with this object.
|
| :rtype: float
|
| set_logprob(self, logprob)
| Set the log probability associated with this object to
| ``logprob``. I.e., set the probability associated with this
| object to ``2**(logprob)``.
|
| :param logprob: The new log probability
| :type logprob: float
|
| set_prob(self, prob)
| Set the probability associated with this object to ``prob``.
|
| :param prob: The new probability
| :type prob: float
class ImmutableTree(Tree)
| Method resolution order:
| ImmutableTree
| Tree
| __builtin__.list
| __builtin__.object
|
| Methods defined here:
|
| __delitem__(self, index)
|
| __delslice__(self, i, j)
|
| __hash__(self)
|
| __iadd__(self, other)
|
| __imul__(self, other)
|
| __init__(self, node, children=None)
|
| __setitem__(self, index, value)
|
| __setslice__(self, i, j, value)
|
| append(self, v)
|
| extend(self, v)
|
| pop(self, v=None)
|
| remove(self, v)
|
| reverse(self)
|
| set_label(self, value)
| Set the node label. This will only succeed the first time the
| node label is set, which should occur in ImmutableTree.__init__().
|
| sort(self)
|
| ----------------------------------------------------------------------
| Methods inherited from Tree:
|
| __add__(self, v)
|
| __eq__(self, other)
|
| __ge__ lambda self, other
|
| __getitem__(self, index)
|
| __gt__ lambda self, other
|
| __le__ lambda self, other
|
| __lt__(self, other)
|
| __mul__(self, v)
|
| __ne__ lambda self, other
| # @total_ordering doesn't work here, since the class inherits from a builtin class
|
| __radd__(self, v)
|
| __repr__(self)
|
| __rmul__(self, v)
|
| __str__(self)
|
| __unicode__ = __str__(self)
|
| chomsky_normal_form(self, factor=u'right', horzMarkov=None, vertMarkov=0, childChar=u'|', parentChar=u'^')
| This method can modify a tree in three ways:
|
| 1. Convert a tree into its Chomsky Normal Form (CNF)
| equivalent -- Every subtree has either two non-terminals
| or one terminal as its children. This process requires
| the creation of more"artificial" non-terminal nodes.
| 2. Markov (vertical) smoothing of children in new artificial
| nodes
| 3. Horizontal (parent) annotation of nodes
|
| :param factor: Right or left factoring method (default = "right")
| :type factor: str = [left|right]
| :param horzMarkov: Markov order for sibling smoothing in artificial nodes (None (default) = include all siblings)
| :type horzMarkov: int | None
| :param vertMarkov: Markov order for parent smoothing (0 (default) = no vertical annotation)
| :type vertMarkov: int | None
| :param childChar: A string used in construction of the artificial nodes, separating the head of the
| original subtree from the child nodes that have yet to be expanded (default = "|")
| :type childChar: str
| :param parentChar: A string used to separate the node representation from its vertical annotation
| :type parentChar: str
|
| collapse_unary(self, collapsePOS=False, collapseRoot=False, joinChar=u'+')
| Collapse subtrees with a single child (ie. unary productions)
| into a new non-terminal (Tree node) joined by 'joinChar'.
| This is useful when working with algorithms that do not allow
| unary productions, and completely removing the unary productions
| would require loss of useful information. The Tree is modified
| directly (since it is passed by reference) and no value is returned.
|
| :param collapsePOS: 'False' (default) will not collapse the parent of leaf nodes (ie.
| Part-of-Speech tags) since they are always unary productions
| :type collapsePOS: bool
| :param collapseRoot: 'False' (default) will not modify the root production
| if it is unary. For the Penn WSJ treebank corpus, this corresponds
| to the TOP -> productions.
| :type collapseRoot: bool
| :param joinChar: A string used to connect collapsed node values (default = "+")
| :type joinChar: str
|
| copy(self, deep=False)
|
| draw(self)
| Open a new window containing a graphical diagram of this tree.
|
| flatten(self)
| Return a flat version of the tree, with all non-root non-terminals removed.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> print(t.flatten())
| (S the dog chased the cat)
|
| :return: a tree consisting of this tree's root connected directly to
| its leaves, omitting all intervening non-terminal nodes.
| :rtype: Tree
|
| freeze(self, leaf_freezer=None)
|
| height(self)
| Return the height of the tree.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> t.height()
| 5
| >>> print(t[0,0])
| (D the)
| >>> t[0,0].height()
| 2
|
| :return: The height of this tree. The height of a tree
| containing no children is 1; the height of a tree
| containing only leaves is 2; and the height of any other
| tree is one plus the maximum of its children's
| heights.
| :rtype: int
|
| label(self)
| Return the node label of the tree.
|
| >>> t = Tree.fromstring('(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))')
| >>> t.label()
| 'S'
|
| :return: the node label (typically a string)
| :rtype: any
|
| leaf_treeposition(self, index)
| :return: The tree position of the ``index``-th leaf in this
| tree. I.e., if ``tp=self.leaf_treeposition(i)``, then
| ``self[tp]==self.leaves()[i]``.
|
| :raise IndexError: If this tree contains fewer than ``index+1``
| leaves, or if ``index<0``.
|
| leaves(self)
| Return the leaves of the tree.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> t.leaves()
| ['the', 'dog', 'chased', 'the', 'cat']
|
| :return: a list containing this tree's leaves.
| The order reflects the order of the
| leaves in the tree's hierarchical structure.
| :rtype: list
|
| pformat(self, margin=70, indent=0, nodesep=u'', parens=u'()', quotes=False)
| :return: A pretty-printed string representation of this tree.
| :rtype: str
| :param margin: The right margin at which to do line-wrapping.
| :type margin: int
| :param indent: The indentation level at which printing
| begins. This number is used to decide how far to indent
| subsequent lines.
| :type indent: int
| :param nodesep: A string that is used to separate the node
| from the children. E.g., the default value ``':'`` gives
| trees like ``(S: (NP: I) (VP: (V: saw) (NP: it)))``.
|
| pformat_latex_qtree(self)
| Returns a representation of the tree compatible with the
| LaTeX qtree package. This consists of the string ``\Tree``
| followed by the tree represented in bracketed notation.
|
| For example, the following result was generated from a parse tree of
| the sentence ``The announcement astounded us``::
|
| \Tree [.I'' [.N'' [.D The ] [.N' [.N announcement ] ] ]
| [.I' [.V'' [.V' [.V astounded ] [.N'' [.N' [.N us ] ] ] ] ] ] ]
|
| See http://www.ling.upenn.edu/advice/latex.html for the LaTeX
| style file for the qtree package.
|
| :return: A latex qtree representation of this tree.
| :rtype: str
|
| pos(self)
| Return a sequence of pos-tagged words extracted from the tree.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> t.pos()
| [('the', 'D'), ('dog', 'N'), ('chased', 'V'), ('the', 'D'), ('cat', 'N')]
|
| :return: a list of tuples containing leaves and pre-terminals (part-of-speech tags).
| The order reflects the order of the leaves in the tree's hierarchical structure.
| :rtype: list(tuple)
|
| pprint(self, **kwargs)
| Print a string representation of this Tree to 'stream'
|
| pretty_print(self, sentence=None, highlight=(), stream=None, **kwargs)
| Pretty-print this tree as ASCII or Unicode art.
| For explanation of the arguments, see the documentation for
| `nltk.treeprettyprinter.TreePrettyPrinter`.
|
| productions(self)
| Generate the productions that correspond to the non-terminal nodes of the tree.
| For each subtree of the form (P: C1 C2 ... Cn) this produces a production of the
| form P -> C1 C2 ... Cn.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> t.productions()
| [S -> NP VP, NP -> D N, D -> 'the', N -> 'dog', VP -> V NP, V -> 'chased',
| NP -> D N, D -> 'the', N -> 'cat']
|
| :rtype: list(Production)
|
| subtrees(self, filter=None)
| Generate all the subtrees of this tree, optionally restricted
| to trees matching the filter function.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> for s in t.subtrees(lambda t: t.height() == 2):
| ... print(s)
| (D the)
| (N dog)
| (V chased)
| (D the)
| (N cat)
|
| :type filter: function
| :param filter: the function to filter all local trees
|
| treeposition_spanning_leaves(self, start, end)
| :return: The tree position of the lowest descendant of this
| tree that dominates ``self.leaves()[start:end]``.
| :raise ValueError: if ``end <= start``
|
| treepositions(self, order=u'preorder')
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> t.treepositions() # doctest: +ELLIPSIS
| [(), (0,), (0, 0), (0, 0, 0), (0, 1), (0, 1, 0), (1,), (1, 0), (1, 0, 0), ...]
| >>> for pos in t.treepositions('leaves'):
| ... t[pos] = t[pos][::-1].upper()
| >>> print(t)
| (S (NP (D EHT) (N GOD)) (VP (V DESAHC) (NP (D EHT) (N TAC))))
|
| :param order: One of: ``preorder``, ``postorder``, ``bothorder``,
| ``leaves``.
|
| un_chomsky_normal_form(self, expandUnary=True, childChar=u'|', parentChar=u'^', unaryChar=u'+')
| This method modifies the tree in three ways:
|
| 1. Transforms a tree in Chomsky Normal Form back to its
| original structure (branching greater than two)
| 2. Removes any parent annotation (if it exists)
| 3. (optional) expands unary subtrees (if previously
| collapsed with collapseUnary(...) )
|
| :param expandUnary: Flag to expand unary or not (default = True)
| :type expandUnary: bool
| :param childChar: A string separating the head node from its children in an artificial node (default = "|")
| :type childChar: str
| :param parentChar: A sting separating the node label from its parent annotation (default = "^")
| :type parentChar: str
| :param unaryChar: A string joining two non-terminals in a unary production (default = "+")
| :type unaryChar: str
|
| unicode_repr = __repr__(self)
|
| ----------------------------------------------------------------------
| Class methods inherited from Tree:
|
| convert(cls, tree) from __builtin__.type
| Convert a tree between different subtypes of Tree. ``cls`` determines
| which class will be used to encode the new tree.
|
| :type tree: Tree
| :param tree: The tree that should be converted.
| :return: The new Tree.
|
| fromstring(cls, s, brackets=u'()', read_node=None, read_leaf=None, node_pattern=None, leaf_pattern=None, remove_empty_top_bracketing=False) from __builtin__.type
| Read a bracketed tree string and return the resulting tree.
| Trees are represented as nested brackettings, such as::
|
| (S (NP (NNP John)) (VP (V runs)))
|
| :type s: str
| :param s: The string to read
|
| :type brackets: str (length=2)
| :param brackets: The bracket characters used to mark the
| beginning and end of trees and subtrees.
|
| :type read_node: function
| :type read_leaf: function
| :param read_node, read_leaf: If specified, these functions
| are applied to the substrings of ``s`` corresponding to
| nodes and leaves (respectively) to obtain the values for
| those nodes and leaves. They should have the following
| signature:
|
| read_node(str) -> value
|
| For example, these functions could be used to process nodes
| and leaves whose values should be some type other than
| string (such as ``FeatStruct``).
| Note that by default, node strings and leaf strings are
| delimited by whitespace and brackets; to override this
| default, use the ``node_pattern`` and ``leaf_pattern``
| arguments.
|
| :type node_pattern: str
| :type leaf_pattern: str
| :param node_pattern, leaf_pattern: Regular expression patterns
| used to find node and leaf substrings in ``s``. By
| default, both nodes patterns are defined to match any
| sequence of non-whitespace non-bracket characters.
|
| :type remove_empty_top_bracketing: bool
| :param remove_empty_top_bracketing: If the resulting tree has
| an empty node label, and is length one, then return its
| single child instead. This is useful for treebank trees,
| which sometimes contain an extra level of bracketing.
|
| :return: A tree corresponding to the string representation ``s``.
| If this class method is called using a subclass of Tree,
| then it will return a tree of that type.
| :rtype: Tree
|
| ----------------------------------------------------------------------
| Data descriptors inherited from Tree:
|
| __dict__
| dictionary for instance variables (if defined)
|
| __weakref__
| list of weak references to the object (if defined)
|
| node
| Outdated method to access the node value; use the label() method instead.
|
| ----------------------------------------------------------------------
| Methods inherited from __builtin__.list:
|
| __contains__(...)
| x.__contains__(y) <==> y in x
|
| __getattribute__(...)
| x.__getattribute__('name') <==> x.name
|
| __getslice__(...)
| x.__getslice__(i, j) <==> x[i:j]
|
| Use of negative indices is not supported.
|
| __iter__(...)
| x.__iter__() <==> iter(x)
|
| __len__(...)
| x.__len__() <==> len(x)
|
| __reversed__(...)
| L.__reversed__() -- return a reverse iterator over the list
|
| __sizeof__(...)
| L.__sizeof__() -- size of L in memory, in bytes
|
| count(...)
| L.count(value) -> integer -- return number of occurrences of value
|
| index(...)
| L.index(value, [start, [stop]]) -> integer -- return first index of value.
| Raises ValueError if the value is not present.
|
| insert(...)
| L.insert(index, object) -- insert object before index
|
| ----------------------------------------------------------------------
| Data and other attributes inherited from __builtin__.list:
|
| __new__ = <built-in method __new__ of type object>
| T.__new__(S, ...) -> a new object with type S, a subtype of T
class MultiParentedTree(AbstractParentedTree)
| A ``Tree`` that automatically maintains parent pointers for
| multi-parented trees. The following are methods for querying the
| structure of a multi-parented tree: ``parents()``, ``parent_indices()``,
| ``left_siblings()``, ``right_siblings()``, ``roots``, ``treepositions``.
|
| Each ``MultiParentedTree`` may have zero or more parents. In
| particular, subtrees may be shared. If a single
| ``MultiParentedTree`` is used as multiple children of the same
| parent, then that parent will appear multiple times in its
| ``parents()`` method.
|
| ``MultiParentedTrees`` should never be used in the same tree as
| ``Trees`` or ``ParentedTrees``. Mixing tree implementations may
| result in incorrect parent pointers and in ``TypeError`` exceptions.
|
| Method resolution order:
| MultiParentedTree
| AbstractParentedTree
| Tree
| __builtin__.list
| __builtin__.object
|
| Methods defined here:
|
| __init__(self, node, children=None)
|
| left_siblings(self)
| A list of all left siblings of this tree, in any of its parent
| trees. A tree may be its own left sibling if it is used as
| multiple contiguous children of the same parent. A tree may
| appear multiple times in this list if it is the left sibling
| of this tree with respect to multiple parents.
|
| :type: list(MultiParentedTree)
|
| parent_indices(self, parent)
| Return a list of the indices where this tree occurs as a child
| of ``parent``. If this child does not occur as a child of
| ``parent``, then the empty list is returned. The following is
| always true::
|
| for parent_index in ptree.parent_indices(parent):
| parent[parent_index] is ptree
|
| parents(self)
| The set of parents of this tree. If this tree has no parents,
| then ``parents`` is the empty set. To check if a tree is used
| as multiple children of the same parent, use the
| ``parent_indices()`` method.
|
| :type: list(MultiParentedTree)
|
| right_siblings(self)
| A list of all right siblings of this tree, in any of its parent
| trees. A tree may be its own right sibling if it is used as
| multiple contiguous children of the same parent. A tree may
| appear multiple times in this list if it is the right sibling
| of this tree with respect to multiple parents.
|
| :type: list(MultiParentedTree)
|
| roots(self)
| The set of all roots of this tree. This set is formed by
| tracing all possible parent paths until trees with no parents
| are found.
|
| :type: list(MultiParentedTree)
|
| treepositions(self, root)
| Return a list of all tree positions that can be used to reach
| this multi-parented tree starting from ``root``. I.e., the
| following is always true::
|
| for treepos in ptree.treepositions(root):
| root[treepos] is ptree
|
| ----------------------------------------------------------------------
| Methods inherited from AbstractParentedTree:
|
| __delitem__(self, index)
|
| __delslice__(self, start, stop)
|
| __getslice__(self, start, stop)
|
| __setitem__(self, index, value)
|
| __setslice__(self, start, stop, value)
|
| append(self, child)
|
| extend(self, children)
|
| insert(self, index, child)
|
| pop(self, index=-1)
|
| remove(self, child)
| # n.b.: like `list`, this is done by equality, not identity!
| # To remove a specific child, use del ptree[i].
|
| ----------------------------------------------------------------------
| Methods inherited from Tree:
|
| __add__(self, v)
|
| __eq__(self, other)
|
| __ge__ lambda self, other
|
| __getitem__(self, index)
|
| __gt__ lambda self, other
|
| __le__ lambda self, other
|
| __lt__(self, other)
|
| __mul__(self, v)
|
| __ne__ lambda self, other
| # @total_ordering doesn't work here, since the class inherits from a builtin class
|
| __radd__(self, v)
|
| __repr__(self)
|
| __rmul__(self, v)
|
| __str__(self)
|
| __unicode__ = __str__(self)
|
| chomsky_normal_form(self, factor=u'right', horzMarkov=None, vertMarkov=0, childChar=u'|', parentChar=u'^')
| This method can modify a tree in three ways:
|
| 1. Convert a tree into its Chomsky Normal Form (CNF)
| equivalent -- Every subtree has either two non-terminals
| or one terminal as its children. This process requires
| the creation of more"artificial" non-terminal nodes.
| 2. Markov (vertical) smoothing of children in new artificial
| nodes
| 3. Horizontal (parent) annotation of nodes
|
| :param factor: Right or left factoring method (default = "right")
| :type factor: str = [left|right]
| :param horzMarkov: Markov order for sibling smoothing in artificial nodes (None (default) = include all siblings)
| :type horzMarkov: int | None
| :param vertMarkov: Markov order for parent smoothing (0 (default) = no vertical annotation)
| :type vertMarkov: int | None
| :param childChar: A string used in construction of the artificial nodes, separating the head of the
| original subtree from the child nodes that have yet to be expanded (default = "|")
| :type childChar: str
| :param parentChar: A string used to separate the node representation from its vertical annotation
| :type parentChar: str
|
| collapse_unary(self, collapsePOS=False, collapseRoot=False, joinChar=u'+')
| Collapse subtrees with a single child (ie. unary productions)
| into a new non-terminal (Tree node) joined by 'joinChar'.
| This is useful when working with algorithms that do not allow
| unary productions, and completely removing the unary productions
| would require loss of useful information. The Tree is modified
| directly (since it is passed by reference) and no value is returned.
|
| :param collapsePOS: 'False' (default) will not collapse the parent of leaf nodes (ie.
| Part-of-Speech tags) since they are always unary productions
| :type collapsePOS: bool
| :param collapseRoot: 'False' (default) will not modify the root production
| if it is unary. For the Penn WSJ treebank corpus, this corresponds
| to the TOP -> productions.
| :type collapseRoot: bool
| :param joinChar: A string used to connect collapsed node values (default = "+")
| :type joinChar: str
|
| copy(self, deep=False)
|
| draw(self)
| Open a new window containing a graphical diagram of this tree.
|
| flatten(self)
| Return a flat version of the tree, with all non-root non-terminals removed.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> print(t.flatten())
| (S the dog chased the cat)
|
| :return: a tree consisting of this tree's root connected directly to
| its leaves, omitting all intervening non-terminal nodes.
| :rtype: Tree
|
| freeze(self, leaf_freezer=None)
|
| height(self)
| Return the height of the tree.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> t.height()
| 5
| >>> print(t[0,0])
| (D the)
| >>> t[0,0].height()
| 2
|
| :return: The height of this tree. The height of a tree
| containing no children is 1; the height of a tree
| containing only leaves is 2; and the height of any other
| tree is one plus the maximum of its children's
| heights.
| :rtype: int
|
| label(self)
| Return the node label of the tree.
|
| >>> t = Tree.fromstring('(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))')
| >>> t.label()
| 'S'
|
| :return: the node label (typically a string)
| :rtype: any
|
| leaf_treeposition(self, index)
| :return: The tree position of the ``index``-th leaf in this
| tree. I.e., if ``tp=self.leaf_treeposition(i)``, then
| ``self[tp]==self.leaves()[i]``.
|
| :raise IndexError: If this tree contains fewer than ``index+1``
| leaves, or if ``index<0``.
|
| leaves(self)
| Return the leaves of the tree.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> t.leaves()
| ['the', 'dog', 'chased', 'the', 'cat']
|
| :return: a list containing this tree's leaves.
| The order reflects the order of the
| leaves in the tree's hierarchical structure.
| :rtype: list
|
| pformat(self, margin=70, indent=0, nodesep=u'', parens=u'()', quotes=False)
| :return: A pretty-printed string representation of this tree.
| :rtype: str
| :param margin: The right margin at which to do line-wrapping.
| :type margin: int
| :param indent: The indentation level at which printing
| begins. This number is used to decide how far to indent
| subsequent lines.
| :type indent: int
| :param nodesep: A string that is used to separate the node
| from the children. E.g., the default value ``':'`` gives
| trees like ``(S: (NP: I) (VP: (V: saw) (NP: it)))``.
|
| pformat_latex_qtree(self)
| Returns a representation of the tree compatible with the
| LaTeX qtree package. This consists of the string ``\Tree``
| followed by the tree represented in bracketed notation.
|
| For example, the following result was generated from a parse tree of
| the sentence ``The announcement astounded us``::
|
| \Tree [.I'' [.N'' [.D The ] [.N' [.N announcement ] ] ]
| [.I' [.V'' [.V' [.V astounded ] [.N'' [.N' [.N us ] ] ] ] ] ] ]
|
| See http://www.ling.upenn.edu/advice/latex.html for the LaTeX
| style file for the qtree package.
|
| :return: A latex qtree representation of this tree.
| :rtype: str
|
| pos(self)
| Return a sequence of pos-tagged words extracted from the tree.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> t.pos()
| [('the', 'D'), ('dog', 'N'), ('chased', 'V'), ('the', 'D'), ('cat', 'N')]
|
| :return: a list of tuples containing leaves and pre-terminals (part-of-speech tags).
| The order reflects the order of the leaves in the tree's hierarchical structure.
| :rtype: list(tuple)
|
| pprint(self, **kwargs)
| Print a string representation of this Tree to 'stream'
|
| pretty_print(self, sentence=None, highlight=(), stream=None, **kwargs)
| Pretty-print this tree as ASCII or Unicode art.
| For explanation of the arguments, see the documentation for
| `nltk.treeprettyprinter.TreePrettyPrinter`.
|
| productions(self)
| Generate the productions that correspond to the non-terminal nodes of the tree.
| For each subtree of the form (P: C1 C2 ... Cn) this produces a production of the
| form P -> C1 C2 ... Cn.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> t.productions()
| [S -> NP VP, NP -> D N, D -> 'the', N -> 'dog', VP -> V NP, V -> 'chased',
| NP -> D N, D -> 'the', N -> 'cat']
|
| :rtype: list(Production)
|
| set_label(self, label)
| Set the node label of the tree.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> t.set_label("T")
| >>> print(t)
| (T (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))
|
| :param label: the node label (typically a string)
| :type label: any
|
| subtrees(self, filter=None)
| Generate all the subtrees of this tree, optionally restricted
| to trees matching the filter function.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> for s in t.subtrees(lambda t: t.height() == 2):
| ... print(s)
| (D the)
| (N dog)
| (V chased)
| (D the)
| (N cat)
|
| :type filter: function
| :param filter: the function to filter all local trees
|
| treeposition_spanning_leaves(self, start, end)
| :return: The tree position of the lowest descendant of this
| tree that dominates ``self.leaves()[start:end]``.
| :raise ValueError: if ``end <= start``
|
| un_chomsky_normal_form(self, expandUnary=True, childChar=u'|', parentChar=u'^', unaryChar=u'+')
| This method modifies the tree in three ways:
|
| 1. Transforms a tree in Chomsky Normal Form back to its
| original structure (branching greater than two)
| 2. Removes any parent annotation (if it exists)
| 3. (optional) expands unary subtrees (if previously
| collapsed with collapseUnary(...) )
|
| :param expandUnary: Flag to expand unary or not (default = True)
| :type expandUnary: bool
| :param childChar: A string separating the head node from its children in an artificial node (default = "|")
| :type childChar: str
| :param parentChar: A sting separating the node label from its parent annotation (default = "^")
| :type parentChar: str
| :param unaryChar: A string joining two non-terminals in a unary production (default = "+")
| :type unaryChar: str
|
| unicode_repr = __repr__(self)
|
| ----------------------------------------------------------------------
| Class methods inherited from Tree:
|
| convert(cls, tree) from __builtin__.type
| Convert a tree between different subtypes of Tree. ``cls`` determines
| which class will be used to encode the new tree.
|
| :type tree: Tree
| :param tree: The tree that should be converted.
| :return: The new Tree.
|
| fromstring(cls, s, brackets=u'()', read_node=None, read_leaf=None, node_pattern=None, leaf_pattern=None, remove_empty_top_bracketing=False) from __builtin__.type
| Read a bracketed tree string and return the resulting tree.
| Trees are represented as nested brackettings, such as::
|
| (S (NP (NNP John)) (VP (V runs)))
|
| :type s: str
| :param s: The string to read
|
| :type brackets: str (length=2)
| :param brackets: The bracket characters used to mark the
| beginning and end of trees and subtrees.
|
| :type read_node: function
| :type read_leaf: function
| :param read_node, read_leaf: If specified, these functions
| are applied to the substrings of ``s`` corresponding to
| nodes and leaves (respectively) to obtain the values for
| those nodes and leaves. They should have the following
| signature:
|
| read_node(str) -> value
|
| For example, these functions could be used to process nodes
| and leaves whose values should be some type other than
| string (such as ``FeatStruct``).
| Note that by default, node strings and leaf strings are
| delimited by whitespace and brackets; to override this
| default, use the ``node_pattern`` and ``leaf_pattern``
| arguments.
|
| :type node_pattern: str
| :type leaf_pattern: str
| :param node_pattern, leaf_pattern: Regular expression patterns
| used to find node and leaf substrings in ``s``. By
| default, both nodes patterns are defined to match any
| sequence of non-whitespace non-bracket characters.
|
| :type remove_empty_top_bracketing: bool
| :param remove_empty_top_bracketing: If the resulting tree has
| an empty node label, and is length one, then return its
| single child instead. This is useful for treebank trees,
| which sometimes contain an extra level of bracketing.
|
| :return: A tree corresponding to the string representation ``s``.
| If this class method is called using a subclass of Tree,
| then it will return a tree of that type.
| :rtype: Tree
|
| ----------------------------------------------------------------------
| Data descriptors inherited from Tree:
|
| __dict__
| dictionary for instance variables (if defined)
|
| __weakref__
| list of weak references to the object (if defined)
|
| node
| Outdated method to access the node value; use the label() method instead.
|
| ----------------------------------------------------------------------
| Methods inherited from __builtin__.list:
|
| __contains__(...)
| x.__contains__(y) <==> y in x
|
| __getattribute__(...)
| x.__getattribute__('name') <==> x.name
|
| __iadd__(...)
| x.__iadd__(y) <==> x+=y
|
| __imul__(...)
| x.__imul__(y) <==> x*=y
|
| __iter__(...)
| x.__iter__() <==> iter(x)
|
| __len__(...)
| x.__len__() <==> len(x)
|
| __reversed__(...)
| L.__reversed__() -- return a reverse iterator over the list
|
| __sizeof__(...)
| L.__sizeof__() -- size of L in memory, in bytes
|
| count(...)
| L.count(value) -> integer -- return number of occurrences of value
|
| index(...)
| L.index(value, [start, [stop]]) -> integer -- return first index of value.
| Raises ValueError if the value is not present.
|
| reverse(...)
| L.reverse() -- reverse *IN PLACE*
|
| sort(...)
| L.sort(cmp=None, key=None, reverse=False) -- stable sort *IN PLACE*;
| cmp(x, y) -> -1, 0, 1
|
| ----------------------------------------------------------------------
| Data and other attributes inherited from __builtin__.list:
|
| __hash__ = None
|
| __new__ = <built-in method __new__ of type object>
| T.__new__(S, ...) -> a new object with type S, a subtype of T
class ParentedTree(AbstractParentedTree)
| A ``Tree`` that automatically maintains parent pointers for
| single-parented trees. The following are methods for querying
| the structure of a parented tree: ``parent``, ``parent_index``,
| ``left_sibling``, ``right_sibling``, ``root``, ``treeposition``.
|
| Each ``ParentedTree`` may have at most one parent. In
| particular, subtrees may not be shared. Any attempt to reuse a
| single ``ParentedTree`` as a child of more than one parent (or
| as multiple children of the same parent) will cause a
| ``ValueError`` exception to be raised.
|
| ``ParentedTrees`` should never be used in the same tree as ``Trees``
| or ``MultiParentedTrees``. Mixing tree implementations may result
| in incorrect parent pointers and in ``TypeError`` exceptions.
|
| Method resolution order:
| ParentedTree
| AbstractParentedTree
| Tree
| __builtin__.list
| __builtin__.object
|
| Methods defined here:
|
| __init__(self, node, children=None)
|
| left_sibling(self)
| The left sibling of this tree, or None if it has none.
|
| parent(self)
| The parent of this tree, or None if it has no parent.
|
| parent_index(self)
| The index of this tree in its parent. I.e.,
| ``ptree.parent()[ptree.parent_index()] is ptree``. Note that
| ``ptree.parent_index()`` is not necessarily equal to
| ``ptree.parent.index(ptree)``, since the ``index()`` method
| returns the first child that is equal to its argument.
|
| right_sibling(self)
| The right sibling of this tree, or None if it has none.
|
| root(self)
| The root of this tree. I.e., the unique ancestor of this tree
| whose parent is None. If ``ptree.parent()`` is None, then
| ``ptree`` is its own root.
|
| treeposition(self)
| The tree position of this tree, relative to the root of the
| tree. I.e., ``ptree.root[ptree.treeposition] is ptree``.
|
| ----------------------------------------------------------------------
| Methods inherited from AbstractParentedTree:
|
| __delitem__(self, index)
|
| __delslice__(self, start, stop)
|
| __getslice__(self, start, stop)
|
| __setitem__(self, index, value)
|
| __setslice__(self, start, stop, value)
|
| append(self, child)
|
| extend(self, children)
|
| insert(self, index, child)
|
| pop(self, index=-1)
|
| remove(self, child)
| # n.b.: like `list`, this is done by equality, not identity!
| # To remove a specific child, use del ptree[i].
|
| ----------------------------------------------------------------------
| Methods inherited from Tree:
|
| __add__(self, v)
|
| __eq__(self, other)
|
| __ge__ lambda self, other
|
| __getitem__(self, index)
|
| __gt__ lambda self, other
|
| __le__ lambda self, other
|
| __lt__(self, other)
|
| __mul__(self, v)
|
| __ne__ lambda self, other
| # @total_ordering doesn't work here, since the class inherits from a builtin class
|
| __radd__(self, v)
|
| __repr__(self)
|
| __rmul__(self, v)
|
| __str__(self)
|
| __unicode__ = __str__(self)
|
| chomsky_normal_form(self, factor=u'right', horzMarkov=None, vertMarkov=0, childChar=u'|', parentChar=u'^')
| This method can modify a tree in three ways:
|
| 1. Convert a tree into its Chomsky Normal Form (CNF)
| equivalent -- Every subtree has either two non-terminals
| or one terminal as its children. This process requires
| the creation of more"artificial" non-terminal nodes.
| 2. Markov (vertical) smoothing of children in new artificial
| nodes
| 3. Horizontal (parent) annotation of nodes
|
| :param factor: Right or left factoring method (default = "right")
| :type factor: str = [left|right]
| :param horzMarkov: Markov order for sibling smoothing in artificial nodes (None (default) = include all siblings)
| :type horzMarkov: int | None
| :param vertMarkov: Markov order for parent smoothing (0 (default) = no vertical annotation)
| :type vertMarkov: int | None
| :param childChar: A string used in construction of the artificial nodes, separating the head of the
| original subtree from the child nodes that have yet to be expanded (default = "|")
| :type childChar: str
| :param parentChar: A string used to separate the node representation from its vertical annotation
| :type parentChar: str
|
| collapse_unary(self, collapsePOS=False, collapseRoot=False, joinChar=u'+')
| Collapse subtrees with a single child (ie. unary productions)
| into a new non-terminal (Tree node) joined by 'joinChar'.
| This is useful when working with algorithms that do not allow
| unary productions, and completely removing the unary productions
| would require loss of useful information. The Tree is modified
| directly (since it is passed by reference) and no value is returned.
|
| :param collapsePOS: 'False' (default) will not collapse the parent of leaf nodes (ie.
| Part-of-Speech tags) since they are always unary productions
| :type collapsePOS: bool
| :param collapseRoot: 'False' (default) will not modify the root production
| if it is unary. For the Penn WSJ treebank corpus, this corresponds
| to the TOP -> productions.
| :type collapseRoot: bool
| :param joinChar: A string used to connect collapsed node values (default = "+")
| :type joinChar: str
|
| copy(self, deep=False)
|
| draw(self)
| Open a new window containing a graphical diagram of this tree.
|
| flatten(self)
| Return a flat version of the tree, with all non-root non-terminals removed.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> print(t.flatten())
| (S the dog chased the cat)
|
| :return: a tree consisting of this tree's root connected directly to
| its leaves, omitting all intervening non-terminal nodes.
| :rtype: Tree
|
| freeze(self, leaf_freezer=None)
|
| height(self)
| Return the height of the tree.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> t.height()
| 5
| >>> print(t[0,0])
| (D the)
| >>> t[0,0].height()
| 2
|
| :return: The height of this tree. The height of a tree
| containing no children is 1; the height of a tree
| containing only leaves is 2; and the height of any other
| tree is one plus the maximum of its children's
| heights.
| :rtype: int
|
| label(self)
| Return the node label of the tree.
|
| >>> t = Tree.fromstring('(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))')
| >>> t.label()
| 'S'
|
| :return: the node label (typically a string)
| :rtype: any
|
| leaf_treeposition(self, index)
| :return: The tree position of the ``index``-th leaf in this
| tree. I.e., if ``tp=self.leaf_treeposition(i)``, then
| ``self[tp]==self.leaves()[i]``.
|
| :raise IndexError: If this tree contains fewer than ``index+1``
| leaves, or if ``index<0``.
|
| leaves(self)
| Return the leaves of the tree.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> t.leaves()
| ['the', 'dog', 'chased', 'the', 'cat']
|
| :return: a list containing this tree's leaves.
| The order reflects the order of the
| leaves in the tree's hierarchical structure.
| :rtype: list
|
| pformat(self, margin=70, indent=0, nodesep=u'', parens=u'()', quotes=False)
| :return: A pretty-printed string representation of this tree.
| :rtype: str
| :param margin: The right margin at which to do line-wrapping.
| :type margin: int
| :param indent: The indentation level at which printing
| begins. This number is used to decide how far to indent
| subsequent lines.
| :type indent: int
| :param nodesep: A string that is used to separate the node
| from the children. E.g., the default value ``':'`` gives
| trees like ``(S: (NP: I) (VP: (V: saw) (NP: it)))``.
|
| pformat_latex_qtree(self)
| Returns a representation of the tree compatible with the
| LaTeX qtree package. This consists of the string ``\Tree``
| followed by the tree represented in bracketed notation.
|
| For example, the following result was generated from a parse tree of
| the sentence ``The announcement astounded us``::
|
| \Tree [.I'' [.N'' [.D The ] [.N' [.N announcement ] ] ]
| [.I' [.V'' [.V' [.V astounded ] [.N'' [.N' [.N us ] ] ] ] ] ] ]
|
| See http://www.ling.upenn.edu/advice/latex.html for the LaTeX
| style file for the qtree package.
|
| :return: A latex qtree representation of this tree.
| :rtype: str
|
| pos(self)
| Return a sequence of pos-tagged words extracted from the tree.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> t.pos()
| [('the', 'D'), ('dog', 'N'), ('chased', 'V'), ('the', 'D'), ('cat', 'N')]
|
| :return: a list of tuples containing leaves and pre-terminals (part-of-speech tags).
| The order reflects the order of the leaves in the tree's hierarchical structure.
| :rtype: list(tuple)
|
| pprint(self, **kwargs)
| Print a string representation of this Tree to 'stream'
|
| pretty_print(self, sentence=None, highlight=(), stream=None, **kwargs)
| Pretty-print this tree as ASCII or Unicode art.
| For explanation of the arguments, see the documentation for
| `nltk.treeprettyprinter.TreePrettyPrinter`.
|
| productions(self)
| Generate the productions that correspond to the non-terminal nodes of the tree.
| For each subtree of the form (P: C1 C2 ... Cn) this produces a production of the
| form P -> C1 C2 ... Cn.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> t.productions()
| [S -> NP VP, NP -> D N, D -> 'the', N -> 'dog', VP -> V NP, V -> 'chased',
| NP -> D N, D -> 'the', N -> 'cat']
|
| :rtype: list(Production)
|
| set_label(self, label)
| Set the node label of the tree.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> t.set_label("T")
| >>> print(t)
| (T (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))
|
| :param label: the node label (typically a string)
| :type label: any
|
| subtrees(self, filter=None)
| Generate all the subtrees of this tree, optionally restricted
| to trees matching the filter function.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> for s in t.subtrees(lambda t: t.height() == 2):
| ... print(s)
| (D the)
| (N dog)
| (V chased)
| (D the)
| (N cat)
|
| :type filter: function
| :param filter: the function to filter all local trees
|
| treeposition_spanning_leaves(self, start, end)
| :return: The tree position of the lowest descendant of this
| tree that dominates ``self.leaves()[start:end]``.
| :raise ValueError: if ``end <= start``
|
| treepositions(self, order=u'preorder')
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> t.treepositions() # doctest: +ELLIPSIS
| [(), (0,), (0, 0), (0, 0, 0), (0, 1), (0, 1, 0), (1,), (1, 0), (1, 0, 0), ...]
| >>> for pos in t.treepositions('leaves'):
| ... t[pos] = t[pos][::-1].upper()
| >>> print(t)
| (S (NP (D EHT) (N GOD)) (VP (V DESAHC) (NP (D EHT) (N TAC))))
|
| :param order: One of: ``preorder``, ``postorder``, ``bothorder``,
| ``leaves``.
|
| un_chomsky_normal_form(self, expandUnary=True, childChar=u'|', parentChar=u'^', unaryChar=u'+')
| This method modifies the tree in three ways:
|
| 1. Transforms a tree in Chomsky Normal Form back to its
| original structure (branching greater than two)
| 2. Removes any parent annotation (if it exists)
| 3. (optional) expands unary subtrees (if previously
| collapsed with collapseUnary(...) )
|
| :param expandUnary: Flag to expand unary or not (default = True)
| :type expandUnary: bool
| :param childChar: A string separating the head node from its children in an artificial node (default = "|")
| :type childChar: str
| :param parentChar: A sting separating the node label from its parent annotation (default = "^")
| :type parentChar: str
| :param unaryChar: A string joining two non-terminals in a unary production (default = "+")
| :type unaryChar: str
|
| unicode_repr = __repr__(self)
|
| ----------------------------------------------------------------------
| Class methods inherited from Tree:
|
| convert(cls, tree) from __builtin__.type
| Convert a tree between different subtypes of Tree. ``cls`` determines
| which class will be used to encode the new tree.
|
| :type tree: Tree
| :param tree: The tree that should be converted.
| :return: The new Tree.
|
| fromstring(cls, s, brackets=u'()', read_node=None, read_leaf=None, node_pattern=None, leaf_pattern=None, remove_empty_top_bracketing=False) from __builtin__.type
| Read a bracketed tree string and return the resulting tree.
| Trees are represented as nested brackettings, such as::
|
| (S (NP (NNP John)) (VP (V runs)))
|
| :type s: str
| :param s: The string to read
|
| :type brackets: str (length=2)
| :param brackets: The bracket characters used to mark the
| beginning and end of trees and subtrees.
|
| :type read_node: function
| :type read_leaf: function
| :param read_node, read_leaf: If specified, these functions
| are applied to the substrings of ``s`` corresponding to
| nodes and leaves (respectively) to obtain the values for
| those nodes and leaves. They should have the following
| signature:
|
| read_node(str) -> value
|
| For example, these functions could be used to process nodes
| and leaves whose values should be some type other than
| string (such as ``FeatStruct``).
| Note that by default, node strings and leaf strings are
| delimited by whitespace and brackets; to override this
| default, use the ``node_pattern`` and ``leaf_pattern``
| arguments.
|
| :type node_pattern: str
| :type leaf_pattern: str
| :param node_pattern, leaf_pattern: Regular expression patterns
| used to find node and leaf substrings in ``s``. By
| default, both nodes patterns are defined to match any
| sequence of non-whitespace non-bracket characters.
|
| :type remove_empty_top_bracketing: bool
| :param remove_empty_top_bracketing: If the resulting tree has
| an empty node label, and is length one, then return its
| single child instead. This is useful for treebank trees,
| which sometimes contain an extra level of bracketing.
|
| :return: A tree corresponding to the string representation ``s``.
| If this class method is called using a subclass of Tree,
| then it will return a tree of that type.
| :rtype: Tree
|
| ----------------------------------------------------------------------
| Data descriptors inherited from Tree:
|
| __dict__
| dictionary for instance variables (if defined)
|
| __weakref__
| list of weak references to the object (if defined)
|
| node
| Outdated method to access the node value; use the label() method instead.
|
| ----------------------------------------------------------------------
| Methods inherited from __builtin__.list:
|
| __contains__(...)
| x.__contains__(y) <==> y in x
|
| __getattribute__(...)
| x.__getattribute__('name') <==> x.name
|
| __iadd__(...)
| x.__iadd__(y) <==> x+=y
|
| __imul__(...)
| x.__imul__(y) <==> x*=y
|
| __iter__(...)
| x.__iter__() <==> iter(x)
|
| __len__(...)
| x.__len__() <==> len(x)
|
| __reversed__(...)
| L.__reversed__() -- return a reverse iterator over the list
|
| __sizeof__(...)
| L.__sizeof__() -- size of L in memory, in bytes
|
| count(...)
| L.count(value) -> integer -- return number of occurrences of value
|
| index(...)
| L.index(value, [start, [stop]]) -> integer -- return first index of value.
| Raises ValueError if the value is not present.
|
| reverse(...)
| L.reverse() -- reverse *IN PLACE*
|
| sort(...)
| L.sort(cmp=None, key=None, reverse=False) -- stable sort *IN PLACE*;
| cmp(x, y) -> -1, 0, 1
|
| ----------------------------------------------------------------------
| Data and other attributes inherited from __builtin__.list:
|
| __hash__ = None
|
| __new__ = <built-in method __new__ of type object>
| T.__new__(S, ...) -> a new object with type S, a subtype of T
class ProbabilisticMixIn(__builtin__.object)
| A mix-in class to associate probabilities with other classes
| (trees, rules, etc.). To use the ``ProbabilisticMixIn`` class,
| define a new class that derives from an existing class and from
| ProbabilisticMixIn. You will need to define a new constructor for
| the new class, which explicitly calls the constructors of both its
| parent classes. For example:
|
| >>> from nltk.probability import ProbabilisticMixIn
| >>> class A:
| ... def __init__(self, x, y): self.data = (x,y)
| ...
| >>> class ProbabilisticA(A, ProbabilisticMixIn):
| ... def __init__(self, x, y, **prob_kwarg):
| ... A.__init__(self, x, y)
| ... ProbabilisticMixIn.__init__(self, **prob_kwarg)
|
| See the documentation for the ProbabilisticMixIn
| ``constructor<__init__>`` for information about the arguments it
| expects.
|
| You should generally also redefine the string representation
| methods, the comparison methods, and the hashing method.
|
| Methods defined here:
|
| __init__(self, **kwargs)
| Initialize this object's probability. This initializer should
| be called by subclass constructors. ``prob`` should generally be
| the first argument for those constructors.
|
| :param prob: The probability associated with the object.
| :type prob: float
| :param logprob: The log of the probability associated with
| the object.
| :type logprob: float
|
| logprob(self)
| Return ``log(p)``, where ``p`` is the probability associated
| with this object.
|
| :rtype: float
|
| prob(self)
| Return the probability associated with this object.
|
| :rtype: float
|
| set_logprob(self, logprob)
| Set the log probability associated with this object to
| ``logprob``. I.e., set the probability associated with this
| object to ``2**(logprob)``.
|
| :param logprob: The new log probability
| :type logprob: float
|
| set_prob(self, prob)
| Set the probability associated with this object to ``prob``.
|
| :param prob: The new probability
| :type prob: float
|
| ----------------------------------------------------------------------
| Data descriptors defined here:
|
| __dict__
| dictionary for instance variables (if defined)
|
| __weakref__
| list of weak references to the object (if defined)
class ProbabilisticTree(Tree, nltk.probability.ProbabilisticMixIn)
| Method resolution order:
| ProbabilisticTree
| Tree
| __builtin__.list
| nltk.probability.ProbabilisticMixIn
| __builtin__.object
|
| Methods defined here:
|
| __eq__(self, other)
|
| __init__(self, node, children=None, **prob_kwargs)
|
| __lt__(self, other)
|
| __repr__(self)
|
| __str__(self)
|
| __unicode__ = __str__(self)
|
| copy(self, deep=False)
|
| unicode_repr = __repr__(self)
|
| ----------------------------------------------------------------------
| Class methods defined here:
|
| convert(cls, val) from __builtin__.type
|
| ----------------------------------------------------------------------
| Methods inherited from Tree:
|
| __add__(self, v)
|
| __delitem__(self, index)
|
| __ge__ lambda self, other
|
| __getitem__(self, index)
|
| __gt__ lambda self, other
|
| __le__ lambda self, other
|
| __mul__(self, v)
|
| __ne__ lambda self, other
| # @total_ordering doesn't work here, since the class inherits from a builtin class
|
| __radd__(self, v)
|
| __rmul__(self, v)
|
| __setitem__(self, index, value)
|
| chomsky_normal_form(self, factor=u'right', horzMarkov=None, vertMarkov=0, childChar=u'|', parentChar=u'^')
| This method can modify a tree in three ways:
|
| 1. Convert a tree into its Chomsky Normal Form (CNF)
| equivalent -- Every subtree has either two non-terminals
| or one terminal as its children. This process requires
| the creation of more"artificial" non-terminal nodes.
| 2. Markov (vertical) smoothing of children in new artificial
| nodes
| 3. Horizontal (parent) annotation of nodes
|
| :param factor: Right or left factoring method (default = "right")
| :type factor: str = [left|right]
| :param horzMarkov: Markov order for sibling smoothing in artificial nodes (None (default) = include all siblings)
| :type horzMarkov: int | None
| :param vertMarkov: Markov order for parent smoothing (0 (default) = no vertical annotation)
| :type vertMarkov: int | None
| :param childChar: A string used in construction of the artificial nodes, separating the head of the
| original subtree from the child nodes that have yet to be expanded (default = "|")
| :type childChar: str
| :param parentChar: A string used to separate the node representation from its vertical annotation
| :type parentChar: str
|
| collapse_unary(self, collapsePOS=False, collapseRoot=False, joinChar=u'+')
| Collapse subtrees with a single child (ie. unary productions)
| into a new non-terminal (Tree node) joined by 'joinChar'.
| This is useful when working with algorithms that do not allow
| unary productions, and completely removing the unary productions
| would require loss of useful information. The Tree is modified
| directly (since it is passed by reference) and no value is returned.
|
| :param collapsePOS: 'False' (default) will not collapse the parent of leaf nodes (ie.
| Part-of-Speech tags) since they are always unary productions
| :type collapsePOS: bool
| :param collapseRoot: 'False' (default) will not modify the root production
| if it is unary. For the Penn WSJ treebank corpus, this corresponds
| to the TOP -> productions.
| :type collapseRoot: bool
| :param joinChar: A string used to connect collapsed node values (default = "+")
| :type joinChar: str
|
| draw(self)
| Open a new window containing a graphical diagram of this tree.
|
| flatten(self)
| Return a flat version of the tree, with all non-root non-terminals removed.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> print(t.flatten())
| (S the dog chased the cat)
|
| :return: a tree consisting of this tree's root connected directly to
| its leaves, omitting all intervening non-terminal nodes.
| :rtype: Tree
|
| freeze(self, leaf_freezer=None)
|
| height(self)
| Return the height of the tree.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> t.height()
| 5
| >>> print(t[0,0])
| (D the)
| >>> t[0,0].height()
| 2
|
| :return: The height of this tree. The height of a tree
| containing no children is 1; the height of a tree
| containing only leaves is 2; and the height of any other
| tree is one plus the maximum of its children's
| heights.
| :rtype: int
|
| label(self)
| Return the node label of the tree.
|
| >>> t = Tree.fromstring('(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))')
| >>> t.label()
| 'S'
|
| :return: the node label (typically a string)
| :rtype: any
|
| leaf_treeposition(self, index)
| :return: The tree position of the ``index``-th leaf in this
| tree. I.e., if ``tp=self.leaf_treeposition(i)``, then
| ``self[tp]==self.leaves()[i]``.
|
| :raise IndexError: If this tree contains fewer than ``index+1``
| leaves, or if ``index<0``.
|
| leaves(self)
| Return the leaves of the tree.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> t.leaves()
| ['the', 'dog', 'chased', 'the', 'cat']
|
| :return: a list containing this tree's leaves.
| The order reflects the order of the
| leaves in the tree's hierarchical structure.
| :rtype: list
|
| pformat(self, margin=70, indent=0, nodesep=u'', parens=u'()', quotes=False)
| :return: A pretty-printed string representation of this tree.
| :rtype: str
| :param margin: The right margin at which to do line-wrapping.
| :type margin: int
| :param indent: The indentation level at which printing
| begins. This number is used to decide how far to indent
| subsequent lines.
| :type indent: int
| :param nodesep: A string that is used to separate the node
| from the children. E.g., the default value ``':'`` gives
| trees like ``(S: (NP: I) (VP: (V: saw) (NP: it)))``.
|
| pformat_latex_qtree(self)
| Returns a representation of the tree compatible with the
| LaTeX qtree package. This consists of the string ``\Tree``
| followed by the tree represented in bracketed notation.
|
| For example, the following result was generated from a parse tree of
| the sentence ``The announcement astounded us``::
|
| \Tree [.I'' [.N'' [.D The ] [.N' [.N announcement ] ] ]
| [.I' [.V'' [.V' [.V astounded ] [.N'' [.N' [.N us ] ] ] ] ] ] ]
|
| See http://www.ling.upenn.edu/advice/latex.html for the LaTeX
| style file for the qtree package.
|
| :return: A latex qtree representation of this tree.
| :rtype: str
|
| pos(self)
| Return a sequence of pos-tagged words extracted from the tree.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> t.pos()
| [('the', 'D'), ('dog', 'N'), ('chased', 'V'), ('the', 'D'), ('cat', 'N')]
|
| :return: a list of tuples containing leaves and pre-terminals (part-of-speech tags).
| The order reflects the order of the leaves in the tree's hierarchical structure.
| :rtype: list(tuple)
|
| pprint(self, **kwargs)
| Print a string representation of this Tree to 'stream'
|
| pretty_print(self, sentence=None, highlight=(), stream=None, **kwargs)
| Pretty-print this tree as ASCII or Unicode art.
| For explanation of the arguments, see the documentation for
| `nltk.treeprettyprinter.TreePrettyPrinter`.
|
| productions(self)
| Generate the productions that correspond to the non-terminal nodes of the tree.
| For each subtree of the form (P: C1 C2 ... Cn) this produces a production of the
| form P -> C1 C2 ... Cn.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> t.productions()
| [S -> NP VP, NP -> D N, D -> 'the', N -> 'dog', VP -> V NP, V -> 'chased',
| NP -> D N, D -> 'the', N -> 'cat']
|
| :rtype: list(Production)
|
| set_label(self, label)
| Set the node label of the tree.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> t.set_label("T")
| >>> print(t)
| (T (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))
|
| :param label: the node label (typically a string)
| :type label: any
|
| subtrees(self, filter=None)
| Generate all the subtrees of this tree, optionally restricted
| to trees matching the filter function.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> for s in t.subtrees(lambda t: t.height() == 2):
| ... print(s)
| (D the)
| (N dog)
| (V chased)
| (D the)
| (N cat)
|
| :type filter: function
| :param filter: the function to filter all local trees
|
| treeposition_spanning_leaves(self, start, end)
| :return: The tree position of the lowest descendant of this
| tree that dominates ``self.leaves()[start:end]``.
| :raise ValueError: if ``end <= start``
|
| treepositions(self, order=u'preorder')
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> t.treepositions() # doctest: +ELLIPSIS
| [(), (0,), (0, 0), (0, 0, 0), (0, 1), (0, 1, 0), (1,), (1, 0), (1, 0, 0), ...]
| >>> for pos in t.treepositions('leaves'):
| ... t[pos] = t[pos][::-1].upper()
| >>> print(t)
| (S (NP (D EHT) (N GOD)) (VP (V DESAHC) (NP (D EHT) (N TAC))))
|
| :param order: One of: ``preorder``, ``postorder``, ``bothorder``,
| ``leaves``.
|
| un_chomsky_normal_form(self, expandUnary=True, childChar=u'|', parentChar=u'^', unaryChar=u'+')
| This method modifies the tree in three ways:
|
| 1. Transforms a tree in Chomsky Normal Form back to its
| original structure (branching greater than two)
| 2. Removes any parent annotation (if it exists)
| 3. (optional) expands unary subtrees (if previously
| collapsed with collapseUnary(...) )
|
| :param expandUnary: Flag to expand unary or not (default = True)
| :type expandUnary: bool
| :param childChar: A string separating the head node from its children in an artificial node (default = "|")
| :type childChar: str
| :param parentChar: A sting separating the node label from its parent annotation (default = "^")
| :type parentChar: str
| :param unaryChar: A string joining two non-terminals in a unary production (default = "+")
| :type unaryChar: str
|
| ----------------------------------------------------------------------
| Class methods inherited from Tree:
|
| fromstring(cls, s, brackets=u'()', read_node=None, read_leaf=None, node_pattern=None, leaf_pattern=None, remove_empty_top_bracketing=False) from __builtin__.type
| Read a bracketed tree string and return the resulting tree.
| Trees are represented as nested brackettings, such as::
|
| (S (NP (NNP John)) (VP (V runs)))
|
| :type s: str
| :param s: The string to read
|
| :type brackets: str (length=2)
| :param brackets: The bracket characters used to mark the
| beginning and end of trees and subtrees.
|
| :type read_node: function
| :type read_leaf: function
| :param read_node, read_leaf: If specified, these functions
| are applied to the substrings of ``s`` corresponding to
| nodes and leaves (respectively) to obtain the values for
| those nodes and leaves. They should have the following
| signature:
|
| read_node(str) -> value
|
| For example, these functions could be used to process nodes
| and leaves whose values should be some type other than
| string (such as ``FeatStruct``).
| Note that by default, node strings and leaf strings are
| delimited by whitespace and brackets; to override this
| default, use the ``node_pattern`` and ``leaf_pattern``
| arguments.
|
| :type node_pattern: str
| :type leaf_pattern: str
| :param node_pattern, leaf_pattern: Regular expression patterns
| used to find node and leaf substrings in ``s``. By
| default, both nodes patterns are defined to match any
| sequence of non-whitespace non-bracket characters.
|
| :type remove_empty_top_bracketing: bool
| :param remove_empty_top_bracketing: If the resulting tree has
| an empty node label, and is length one, then return its
| single child instead. This is useful for treebank trees,
| which sometimes contain an extra level of bracketing.
|
| :return: A tree corresponding to the string representation ``s``.
| If this class method is called using a subclass of Tree,
| then it will return a tree of that type.
| :rtype: Tree
|
| ----------------------------------------------------------------------
| Data descriptors inherited from Tree:
|
| __dict__
| dictionary for instance variables (if defined)
|
| __weakref__
| list of weak references to the object (if defined)
|
| node
| Outdated method to access the node value; use the label() method instead.
|
| ----------------------------------------------------------------------
| Methods inherited from __builtin__.list:
|
| __contains__(...)
| x.__contains__(y) <==> y in x
|
| __delslice__(...)
| x.__delslice__(i, j) <==> del x[i:j]
|
| Use of negative indices is not supported.
|
| __getattribute__(...)
| x.__getattribute__('name') <==> x.name
|
| __getslice__(...)
| x.__getslice__(i, j) <==> x[i:j]
|
| Use of negative indices is not supported.
|
| __iadd__(...)
| x.__iadd__(y) <==> x+=y
|
| __imul__(...)
| x.__imul__(y) <==> x*=y
|
| __iter__(...)
| x.__iter__() <==> iter(x)
|
| __len__(...)
| x.__len__() <==> len(x)
|
| __reversed__(...)
| L.__reversed__() -- return a reverse iterator over the list
|
| __setslice__(...)
| x.__setslice__(i, j, y) <==> x[i:j]=y
|
| Use of negative indices is not supported.
|
| __sizeof__(...)
| L.__sizeof__() -- size of L in memory, in bytes
|
| append(...)
| L.append(object) -- append object to end
|
| count(...)
| L.count(value) -> integer -- return number of occurrences of value
|
| extend(...)
| L.extend(iterable) -- extend list by appending elements from the iterable
|
| index(...)
| L.index(value, [start, [stop]]) -> integer -- return first index of value.
| Raises ValueError if the value is not present.
|
| insert(...)
| L.insert(index, object) -- insert object before index
|
| pop(...)
| L.pop([index]) -> item -- remove and return item at index (default last).
| Raises IndexError if list is empty or index is out of range.
|
| remove(...)
| L.remove(value) -- remove first occurrence of value.
| Raises ValueError if the value is not present.
|
| reverse(...)
| L.reverse() -- reverse *IN PLACE*
|
| sort(...)
| L.sort(cmp=None, key=None, reverse=False) -- stable sort *IN PLACE*;
| cmp(x, y) -> -1, 0, 1
|
| ----------------------------------------------------------------------
| Data and other attributes inherited from __builtin__.list:
|
| __hash__ = None
|
| __new__ = <built-in method __new__ of type object>
| T.__new__(S, ...) -> a new object with type S, a subtype of T
|
| ----------------------------------------------------------------------
| Methods inherited from nltk.probability.ProbabilisticMixIn:
|
| logprob(self)
| Return ``log(p)``, where ``p`` is the probability associated
| with this object.
|
| :rtype: float
|
| prob(self)
| Return the probability associated with this object.
|
| :rtype: float
|
| set_logprob(self, logprob)
| Set the log probability associated with this object to
| ``logprob``. I.e., set the probability associated with this
| object to ``2**(logprob)``.
|
| :param logprob: The new log probability
| :type logprob: float
|
| set_prob(self, prob)
| Set the probability associated with this object to ``prob``.
|
| :param prob: The new probability
| :type prob: float
class Tree(__builtin__.list)
| A Tree represents a hierarchical grouping of leaves and subtrees.
| For example, each constituent in a syntax tree is represented by a single Tree.
|
| A tree's children are encoded as a list of leaves and subtrees,
| where a leaf is a basic (non-tree) value; and a subtree is a
| nested Tree.
|
| >>> from nltk.tree import Tree
| >>> print(Tree(1, [2, Tree(3, [4]), 5]))
| (1 2 (3 4) 5)
| >>> vp = Tree('VP', [Tree('V', ['saw']),
| ... Tree('NP', ['him'])])
| >>> s = Tree('S', [Tree('NP', ['I']), vp])
| >>> print(s)
| (S (NP I) (VP (V saw) (NP him)))
| >>> print(s[1])
| (VP (V saw) (NP him))
| >>> print(s[1,1])
| (NP him)
| >>> t = Tree.fromstring("(S (NP I) (VP (V saw) (NP him)))")
| >>> s == t
| True
| >>> t[1][1].set_label('X')
| >>> t[1][1].label()
| 'X'
| >>> print(t)
| (S (NP I) (VP (V saw) (X him)))
| >>> t[0], t[1,1] = t[1,1], t[0]
| >>> print(t)
| (S (X him) (VP (V saw) (NP I)))
|
| The length of a tree is the number of children it has.
|
| >>> len(t)
| 2
|
| The set_label() and label() methods allow individual constituents
| to be labeled. For example, syntax trees use this label to specify
| phrase tags, such as "NP" and "VP".
|
| Several Tree methods use "tree positions" to specify
| children or descendants of a tree. Tree positions are defined as
| follows:
|
| - The tree position *i* specifies a Tree's *i*\ th child.
| - The tree position ``()`` specifies the Tree itself.
| - If *p* is the tree position of descendant *d*, then
| *p+i* specifies the *i*\ th child of *d*.
|
| I.e., every tree position is either a single index *i*,
| specifying ``tree[i]``; or a sequence *i1, i2, ..., iN*,
| specifying ``tree[i1][i2]...[iN]``.
|
| Construct a new tree. This constructor can be called in one
| of two ways:
|
| - ``Tree(label, children)`` constructs a new tree with the
| specified label and list of children.
|
| - ``Tree.fromstring(s)`` constructs a new tree by parsing the string ``s``.
|
| Method resolution order:
| Tree
| __builtin__.list
| __builtin__.object
|
| Methods defined here:
|
| __add__(self, v)
|
| __delitem__(self, index)
|
| __eq__(self, other)
|
| __ge__ lambda self, other
|
| __getitem__(self, index)
|
| __gt__ lambda self, other
|
| __init__(self, node, children=None)
|
| __le__ lambda self, other
|
| __lt__(self, other)
|
| __mul__(self, v)
|
| __ne__ lambda self, other
| # @total_ordering doesn't work here, since the class inherits from a builtin class
|
| __radd__(self, v)
|
| __repr__(self)
|
| __rmul__(self, v)
|
| __setitem__(self, index, value)
|
| __str__(self)
|
| __unicode__ = __str__(self)
|
| chomsky_normal_form(self, factor=u'right', horzMarkov=None, vertMarkov=0, childChar=u'|', parentChar=u'^')
| This method can modify a tree in three ways:
|
| 1. Convert a tree into its Chomsky Normal Form (CNF)
| equivalent -- Every subtree has either two non-terminals
| or one terminal as its children. This process requires
| the creation of more"artificial" non-terminal nodes.
| 2. Markov (vertical) smoothing of children in new artificial
| nodes
| 3. Horizontal (parent) annotation of nodes
|
| :param factor: Right or left factoring method (default = "right")
| :type factor: str = [left|right]
| :param horzMarkov: Markov order for sibling smoothing in artificial nodes (None (default) = include all siblings)
| :type horzMarkov: int | None
| :param vertMarkov: Markov order for parent smoothing (0 (default) = no vertical annotation)
| :type vertMarkov: int | None
| :param childChar: A string used in construction of the artificial nodes, separating the head of the
| original subtree from the child nodes that have yet to be expanded (default = "|")
| :type childChar: str
| :param parentChar: A string used to separate the node representation from its vertical annotation
| :type parentChar: str
|
| collapse_unary(self, collapsePOS=False, collapseRoot=False, joinChar=u'+')
| Collapse subtrees with a single child (ie. unary productions)
| into a new non-terminal (Tree node) joined by 'joinChar'.
| This is useful when working with algorithms that do not allow
| unary productions, and completely removing the unary productions
| would require loss of useful information. The Tree is modified
| directly (since it is passed by reference) and no value is returned.
|
| :param collapsePOS: 'False' (default) will not collapse the parent of leaf nodes (ie.
| Part-of-Speech tags) since they are always unary productions
| :type collapsePOS: bool
| :param collapseRoot: 'False' (default) will not modify the root production
| if it is unary. For the Penn WSJ treebank corpus, this corresponds
| to the TOP -> productions.
| :type collapseRoot: bool
| :param joinChar: A string used to connect collapsed node values (default = "+")
| :type joinChar: str
|
| copy(self, deep=False)
|
| draw(self)
| Open a new window containing a graphical diagram of this tree.
|
| flatten(self)
| Return a flat version of the tree, with all non-root non-terminals removed.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> print(t.flatten())
| (S the dog chased the cat)
|
| :return: a tree consisting of this tree's root connected directly to
| its leaves, omitting all intervening non-terminal nodes.
| :rtype: Tree
|
| freeze(self, leaf_freezer=None)
|
| height(self)
| Return the height of the tree.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> t.height()
| 5
| >>> print(t[0,0])
| (D the)
| >>> t[0,0].height()
| 2
|
| :return: The height of this tree. The height of a tree
| containing no children is 1; the height of a tree
| containing only leaves is 2; and the height of any other
| tree is one plus the maximum of its children's
| heights.
| :rtype: int
|
| label(self)
| Return the node label of the tree.
|
| >>> t = Tree.fromstring('(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))')
| >>> t.label()
| 'S'
|
| :return: the node label (typically a string)
| :rtype: any
|
| leaf_treeposition(self, index)
| :return: The tree position of the ``index``-th leaf in this
| tree. I.e., if ``tp=self.leaf_treeposition(i)``, then
| ``self[tp]==self.leaves()[i]``.
|
| :raise IndexError: If this tree contains fewer than ``index+1``
| leaves, or if ``index<0``.
|
| leaves(self)
| Return the leaves of the tree.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> t.leaves()
| ['the', 'dog', 'chased', 'the', 'cat']
|
| :return: a list containing this tree's leaves.
| The order reflects the order of the
| leaves in the tree's hierarchical structure.
| :rtype: list
|
| pformat(self, margin=70, indent=0, nodesep=u'', parens=u'()', quotes=False)
| :return: A pretty-printed string representation of this tree.
| :rtype: str
| :param margin: The right margin at which to do line-wrapping.
| :type margin: int
| :param indent: The indentation level at which printing
| begins. This number is used to decide how far to indent
| subsequent lines.
| :type indent: int
| :param nodesep: A string that is used to separate the node
| from the children. E.g., the default value ``':'`` gives
| trees like ``(S: (NP: I) (VP: (V: saw) (NP: it)))``.
|
| pformat_latex_qtree(self)
| Returns a representation of the tree compatible with the
| LaTeX qtree package. This consists of the string ``\Tree``
| followed by the tree represented in bracketed notation.
|
| For example, the following result was generated from a parse tree of
| the sentence ``The announcement astounded us``::
|
| \Tree [.I'' [.N'' [.D The ] [.N' [.N announcement ] ] ]
| [.I' [.V'' [.V' [.V astounded ] [.N'' [.N' [.N us ] ] ] ] ] ] ]
|
| See http://www.ling.upenn.edu/advice/latex.html for the LaTeX
| style file for the qtree package.
|
| :return: A latex qtree representation of this tree.
| :rtype: str
|
| pos(self)
| Return a sequence of pos-tagged words extracted from the tree.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> t.pos()
| [('the', 'D'), ('dog', 'N'), ('chased', 'V'), ('the', 'D'), ('cat', 'N')]
|
| :return: a list of tuples containing leaves and pre-terminals (part-of-speech tags).
| The order reflects the order of the leaves in the tree's hierarchical structure.
| :rtype: list(tuple)
|
| pprint(self, **kwargs)
| Print a string representation of this Tree to 'stream'
|
| pretty_print(self, sentence=None, highlight=(), stream=None, **kwargs)
| Pretty-print this tree as ASCII or Unicode art.
| For explanation of the arguments, see the documentation for
| `nltk.treeprettyprinter.TreePrettyPrinter`.
|
| productions(self)
| Generate the productions that correspond to the non-terminal nodes of the tree.
| For each subtree of the form (P: C1 C2 ... Cn) this produces a production of the
| form P -> C1 C2 ... Cn.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> t.productions()
| [S -> NP VP, NP -> D N, D -> 'the', N -> 'dog', VP -> V NP, V -> 'chased',
| NP -> D N, D -> 'the', N -> 'cat']
|
| :rtype: list(Production)
|
| set_label(self, label)
| Set the node label of the tree.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> t.set_label("T")
| >>> print(t)
| (T (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))
|
| :param label: the node label (typically a string)
| :type label: any
|
| subtrees(self, filter=None)
| Generate all the subtrees of this tree, optionally restricted
| to trees matching the filter function.
|
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> for s in t.subtrees(lambda t: t.height() == 2):
| ... print(s)
| (D the)
| (N dog)
| (V chased)
| (D the)
| (N cat)
|
| :type filter: function
| :param filter: the function to filter all local trees
|
| treeposition_spanning_leaves(self, start, end)
| :return: The tree position of the lowest descendant of this
| tree that dominates ``self.leaves()[start:end]``.
| :raise ValueError: if ``end <= start``
|
| treepositions(self, order=u'preorder')
| >>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
| >>> t.treepositions() # doctest: +ELLIPSIS
| [(), (0,), (0, 0), (0, 0, 0), (0, 1), (0, 1, 0), (1,), (1, 0), (1, 0, 0), ...]
| >>> for pos in t.treepositions('leaves'):
| ... t[pos] = t[pos][::-1].upper()
| >>> print(t)
| (S (NP (D EHT) (N GOD)) (VP (V DESAHC) (NP (D EHT) (N TAC))))
|
| :param order: One of: ``preorder``, ``postorder``, ``bothorder``,
| ``leaves``.
|
| un_chomsky_normal_form(self, expandUnary=True, childChar=u'|', parentChar=u'^', unaryChar=u'+')
| This method modifies the tree in three ways:
|
| 1. Transforms a tree in Chomsky Normal Form back to its
| original structure (branching greater than two)
| 2. Removes any parent annotation (if it exists)
| 3. (optional) expands unary subtrees (if previously
| collapsed with collapseUnary(...) )
|
| :param expandUnary: Flag to expand unary or not (default = True)
| :type expandUnary: bool
| :param childChar: A string separating the head node from its children in an artificial node (default = "|")
| :type childChar: str
| :param parentChar: A sting separating the node label from its parent annotation (default = "^")
| :type parentChar: str
| :param unaryChar: A string joining two non-terminals in a unary production (default = "+")
| :type unaryChar: str
|
| unicode_repr = __repr__(self)
|
| ----------------------------------------------------------------------
| Class methods defined here:
|
| convert(cls, tree) from __builtin__.type
| Convert a tree between different subtypes of Tree. ``cls`` determines
| which class will be used to encode the new tree.
|
| :type tree: Tree
| :param tree: The tree that should be converted.
| :return: The new Tree.
|
| fromstring(cls, s, brackets=u'()', read_node=None, read_leaf=None, node_pattern=None, leaf_pattern=None, remove_empty_top_bracketing=False) from __builtin__.type
| Read a bracketed tree string and return the resulting tree.
| Trees are represented as nested brackettings, such as::
|
| (S (NP (NNP John)) (VP (V runs)))
|
| :type s: str
| :param s: The string to read
|
| :type brackets: str (length=2)
| :param brackets: The bracket characters used to mark the
| beginning and end of trees and subtrees.
|
| :type read_node: function
| :type read_leaf: function
| :param read_node, read_leaf: If specified, these functions
| are applied to the substrings of ``s`` corresponding to
| nodes and leaves (respectively) to obtain the values for
| those nodes and leaves. They should have the following
| signature:
|
| read_node(str) -> value
|
| For example, these functions could be used to process nodes
| and leaves whose values should be some type other than
| string (such as ``FeatStruct``).
| Note that by default, node strings and leaf strings are
| delimited by whitespace and brackets; to override this
| default, use the ``node_pattern`` and ``leaf_pattern``
| arguments.
|
| :type node_pattern: str
| :type leaf_pattern: str
| :param node_pattern, leaf_pattern: Regular expression patterns
| used to find node and leaf substrings in ``s``. By
| default, both nodes patterns are defined to match any
| sequence of non-whitespace non-bracket characters.
|
| :type remove_empty_top_bracketing: bool
| :param remove_empty_top_bracketing: If the resulting tree has
| an empty node label, and is length one, then return its
| single child instead. This is useful for treebank trees,
| which sometimes contain an extra level of bracketing.
|
| :return: A tree corresponding to the string representation ``s``.
| If this class method is called using a subclass of Tree,
| then it will return a tree of that type.
| :rtype: Tree
|
| ----------------------------------------------------------------------
| Data descriptors defined here:
|
| __dict__
| dictionary for instance variables (if defined)
|
| __weakref__
| list of weak references to the object (if defined)
|
| node
| Outdated method to access the node value; use the label() method instead.
|
| ----------------------------------------------------------------------
| Methods inherited from __builtin__.list:
|
| __contains__(...)
| x.__contains__(y) <==> y in x
|
| __delslice__(...)
| x.__delslice__(i, j) <==> del x[i:j]
|
| Use of negative indices is not supported.
|
| __getattribute__(...)
| x.__getattribute__('name') <==> x.name
|
| __getslice__(...)
| x.__getslice__(i, j) <==> x[i:j]
|
| Use of negative indices is not supported.
|
| __iadd__(...)
| x.__iadd__(y) <==> x+=y
|
| __imul__(...)
| x.__imul__(y) <==> x*=y
|
| __iter__(...)
| x.__iter__() <==> iter(x)
|
| __len__(...)
| x.__len__() <==> len(x)
|
| __reversed__(...)
| L.__reversed__() -- return a reverse iterator over the list
|
| __setslice__(...)
| x.__setslice__(i, j, y) <==> x[i:j]=y
|
| Use of negative indices is not supported.
|
| __sizeof__(...)
| L.__sizeof__() -- size of L in memory, in bytes
|
| append(...)
| L.append(object) -- append object to end
|
| count(...)
| L.count(value) -> integer -- return number of occurrences of value
|
| extend(...)
| L.extend(iterable) -- extend list by appending elements from the iterable
|
| index(...)
| L.index(value, [start, [stop]]) -> integer -- return first index of value.
| Raises ValueError if the value is not present.
|
| insert(...)
| L.insert(index, object) -- insert object before index
|
| pop(...)
| L.pop([index]) -> item -- remove and return item at index (default last).
| Raises IndexError if list is empty or index is out of range.
|
| remove(...)
| L.remove(value) -- remove first occurrence of value.
| Raises ValueError if the value is not present.
|
| reverse(...)
| L.reverse() -- reverse *IN PLACE*
|
| sort(...)
| L.sort(cmp=None, key=None, reverse=False) -- stable sort *IN PLACE*;
| cmp(x, y) -> -1, 0, 1
|
| ----------------------------------------------------------------------
| Data and other attributes inherited from __builtin__.list:
|
| __hash__ = None
|
| __new__ = <built-in method __new__ of type object>
| T.__new__(S, ...) -> a new object with type S, a subtype of T
FUNCTIONS
bracket_parse(s)
Use Tree.read(s, remove_empty_top_bracketing=True) instead.
sinica_parse(s)
Parse a Sinica Treebank string and return a tree. Trees are represented as nested brackettings,
as shown in the following example (X represents a Chinese character):
S(goal:NP(Head:Nep:XX)|theme:NP(Head:Nhaa:X)|quantity:Dab:X|Head:VL2:X)#0(PERIODCATEGORY)
:return: A tree corresponding to the string representation.
:rtype: Tree
:param s: The string to be converted
:type s: str
DATA
__all__ = [u'ImmutableProbabilisticTree', u'ImmutableTree', u'Probabil...
Write a recursive function to traverse a tree and return the depth of the tree, such that a tree with a single node would have depth zero. (Hint: the depth of a subtree is the maximum depth of its children, plus one.)
In [15]:
def depth(node):
if node is None:
return 0
else:
return max(height(node.left), height(node.right)) + 1
In the recursive descent parser demo, experiment with changing the sentence to be parsed by selecting Edit Text in the Edit menu.
In [19]:
grammar = CFG.fromstring("""
S -> NP VP
VP -> V NP | V NP PP
PP -> P NP
V -> "saw" | "ate" | "walked"
NP -> "John" | "Mary" | "Bob" | Det N | Det N PP
Det -> "a" | "an" | "the" | "my"
N -> "man" | "dog" | "cat" | "telescope" | "park"
P -> "in" | "on" | "by" | "with"
""")
sent = "Mary saw Bob".split()
rd_parser = nltk.RecursiveDescentParser(grammar)
for tree in rd_parser.parse(sent):
print tree
(S (NP Mary) (VP (V saw) (NP Bob)))
In [25]:
sent2 = "Mary saw a dog".split()
rd_parser = nltk.RecursiveDescentParser(grammar)
for tree in rd_parser.parse(sent2):
print tree
(S (NP Mary) (VP (V saw) (NP (Det a) (N dog))))
In [28]:
#no match
sent3 = "my dog ate in the park".split()
rd_parser = nltk.RecursiveDescentParser(grammar)
for tree in rd_parser.parse(sent3):
print tree
Can the grammar in grammar1 be used to describe sentences that are more than 20 words in length?
Can you come up with grammatical sentences that have probably never been uttered before? (Take turns with a partner.) What does this tell you about human language?
Content source: nravi89/nlphu
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