Lists | Listas

O que é uma lista?

Uma estrutura de dados heterogenia mutável que preserva ordem dos elementos.

O que eu quero dizer por heterogenia?

2 ou mais diferentes tipos de dados podem estar simultaneamente na lista

O que eu quero dizer por mutável?

Os dados podem ser alterados depois da criação da lista

O que eu quero dizer por preservar ordem?

Os dados permanecem na mesma ordem de sua criação, concatenação, enfim

Exemplos de Listas



In [1]:

    
[] # empty list









    Out[1]:





[]



In [2]:

    
type([])









    Out[2]:





list



In [3]:

    
[1, 2, 3, 4] # list of integers









    Out[3]:





[1, 2, 3, 4]



In [4]:

    
['a', 'b', 'c', 'b'] # list of strs









    Out[4]:





['a', 'b', 'c', 'b']



In [5]:

    
[1, 2, 'a', 'b', [42, 6/7, 'text']] # mixed lists









    Out[5]:





[1, 2, 'a', 'b', [42, 0.8571428571428571, 'text']]

Como criar listas

Exemplo não pythonico de se criar uma Lista



In [2]:

    
lst = []
for i in range(10):
    if i % 2:
        lst.append(i)

print(lst)









    



[1, 3, 5, 7, 9]



In [8]:

    
list(range(10))









    Out[8]:





[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

List Comprehension



In [9]:

    
[1 for i in range(10)]









    Out[9]:





[1, 1, 1, 1, 1, 1, 1, 1, 1, 1]



In [10]:

    
[i for i in range(10) if i % 2]









    Out[10]:





[1, 3, 5, 7, 9]



In [11]:

    
[i ** 2 for i in range(10) if i % 2]









    Out[11]:





[1, 9, 25, 49, 81]



In [12]:

    
["red" if i % 2 else "blue" for i in range(10)]









    Out[12]:





['blue', 'red', 'blue', 'red', 'blue', 'red', 'blue', 'red', 'blue', 'red']



In [13]:

    
["red" if i % 2 else "blue" for i in range(10) if i > 5]









    Out[13]:





['blue', 'red', 'blue', 'red']

Métodos Built-in



In [6]:

    
dir(list) # Available methods









    Out[6]:





['__add__',
 '__class__',
 '__contains__',
 '__delattr__',
 '__delitem__',
 '__dir__',
 '__doc__',
 '__eq__',
 '__format__',
 '__ge__',
 '__getattribute__',
 '__getitem__',
 '__gt__',
 '__hash__',
 '__iadd__',
 '__imul__',
 '__init__',
 '__iter__',
 '__le__',
 '__len__',
 '__lt__',
 '__mul__',
 '__ne__',
 '__new__',
 '__reduce__',
 '__reduce_ex__',
 '__repr__',
 '__reversed__',
 '__rmul__',
 '__setattr__',
 '__setitem__',
 '__sizeof__',
 '__str__',
 '__subclasshook__',
 'append',
 'clear',
 'copy',
 'count',
 'extend',
 'index',
 'insert',
 'pop',
 'remove',
 'reverse',
 'sort']



In [6]:

    
lst = [i for i in range(10) if i % 2] # odd numbers

lst.append(0xc0ffee)
lst









    Out[6]:





[1, 3, 5, 7, 9, 12648430]



In [5]:

    
lst = [i for i in range(10) if i % 2] # odd numbers
new_lst = [i for i in range(10) if i % 2 == 0] # even numbers

lst.extend(new_lst)
lst









    Out[5]:





[1, 3, 5, 7, 9, 0, 2, 4, 6, 8]

Verificando pertinência



In [14]:

    
lst = [1, 3, 5, 7, 9]



In [15]:

    
1 in lst









    Out[15]:





True



In [16]:

    
4 in lst









    Out[16]:





False

Obtendo o Index de determinado elemento



In [7]:

    
lst = [1, 3, 5, 7, 9]



In [8]:

    
lst.index(1) # The first element has index 0









    Out[8]:





0



In [9]:

    
lst.count(3) # How many time the given element appear in such list?









    Out[9]:





1



In [10]:

    
lst.count(4)









    Out[10]:





0



In [11]:

    
#lst.index(4)

#---------------------------------------------------------------------------
#ValueError                                Traceback (most recent call last)
#<ipython-input-14-9e4c9bbba08f> in <module>()
#----> 1 lst.index(4)
#
#ValueError: 4 is not in list



In [21]:

    
sum(lst) # Sum of each element









    Out[21]:





25



In [22]:

    
min(lst)









    Out[22]:





1



In [23]:

    
max(lst)









    Out[23]:





9



In [24]:

    
len(lst)









    Out[24]:





5



In [25]:

    
for i in lst:
    print(i, end=' ')



In [26]:

    
for i in lst:
    i *= 2



In [27]:

    
lst









    Out[27]:





[1, 3, 5, 7, 9]



In [28]:

    
lst * 2









    Out[28]:





[1, 3, 5, 7, 9, 1, 3, 5, 7, 9]



In [29]:

    
#lst + 2

#---------------------------------------------------------------------------
#TypeError                                 Traceback (most recent call last)
#<ipython-input-24-33a94180b36b> in <module>()
#----> 1 lst + 2
#
#TypeError: can only concatenate list (not "int") to list



In [30]:

    
for i in range(len(lst)):
    lst[i] *= 2
lst









    Out[30]:





[2, 6, 10, 14, 18]



In [31]:

    
lst1 = [i for i in range(10) if i % 2]
lst1









    Out[31]:





[1, 3, 5, 7, 9]



In [32]:

    
lst2 = [i * 2 for i in range(10) if i % 2]
lst2









    Out[32]:





[2, 6, 10, 14, 18]



In [33]:

    
lst == lst2









    Out[33]:





True



In [34]:

    
lst is lst2









    Out[34]:





False



In [35]:

    
lst3 = [0] * len(lst1)

for index, value in enumerate(lst1):
    lst3[index] = value * 2
lst3









    Out[35]:





[2, 6, 10, 14, 18]



In [36]:

    
# slicing
lst









    Out[36]:





[2, 6, 10, 14, 18]



In [37]:

    
lst[1:2]









    Out[37]:





[6]



In [38]:

    
lst[:2]









    Out[38]:





[2, 6]



In [39]:

    
lst[1:]









    Out[39]:





[6, 10, 14, 18]



In [40]:

    
lst[:-1]









    Out[40]:





[2, 6, 10, 14]



In [41]:

    
lst[::-1]









    Out[41]:





[18, 14, 10, 6, 2]



In [42]:

    
# indexing
lst









    Out[42]:





[2, 6, 10, 14, 18]



In [43]:

    
len(lst)









    Out[43]:





5



In [44]:

    
lst[0]









    Out[44]:





2



In [45]:

    
lst[len(lst) -1]









    Out[45]:





18



In [46]:

    
lst[-1]









    Out[46]:





18



In [47]:

    
lst[-2]









    Out[47]:





14



In [48]:

    
#lst[13]

#---------------------------------------------------------------------------
#IndexError                                Traceback (most recent call last)
#<ipython-input-44-148af8a65684> in <module>()
#----> 1 lst[13]
#
#IndexError: list index out of range



In [49]:

    
#lst[-9]

#---------------------------------------------------------------------------
#IndexError                                Traceback (most recent call last)
#<ipython-input-45-1b205bc9ac28> in <module>()
#----> 1 lst[-9]
#
#IndexError: list index out of range



In [50]:

    
#lst[1, 3]

#---------------------------------------------------------------------------
#TypeError                                 Traceback (most recent call last)
#<ipython-input-46-b9ef5c5bd789> in <module>()
#----> 1 lst[1, 3]
#
#TypeError: list indices must be integers or slices, not tuple



In [51]:

    
#lst > 3

#---------------------------------------------------------------------------
#TypeError                                 Traceback (most recent call last)
#<ipython-input-47-95398925f275> in <module>()
#----> 1 lst > 3
#
#TypeError: unorderable types: list() > int()



In [52]:

    
lst1









    Out[52]:





[1, 3, 5, 7, 9]



In [53]:

    
lst2









    Out[53]:





[2, 6, 10, 14, 18]



In [54]:

    
lst1 + lst2









    Out[54]:





[1, 3, 5, 7, 9, 2, 6, 10, 14, 18]



In [55]:

    
#lst1 * lst2

#---------------------------------------------------------------------------
#TypeError                                 Traceback (most recent call last)
#<ipython-input-79-67c3fb65c435> in <module>()
#----> 1 lst1 * lst2
#
#TypeError: can't multiply sequence by non-int of type 'list'



In [56]:

    
lst









    Out[56]:





[2, 6, 10, 14, 18]



In [57]:

    
lst1 = [True if _ > 10 else False for _ in lst]
lst1









    Out[57]:





[False, False, False, True, True]



In [58]:

    
#lst[l1]

#---------------------------------------------------------------------------
#TypeError                                 Traceback (most recent call last)
#<ipython-input-82-4bb6def646de> in <module>()
#----> 1 lst[lst1]
#
#TypeError: list indices must be integers or slices, not list



In [59]:

    
lst1 = lst



In [60]:

    
id(lst)









    Out[60]:





140508654019016



In [61]:

    
id(lst1)









    Out[61]:





140508654019016



In [62]:

    
lst1[2] = .79



In [63]:

    
lst









    Out[63]:





[2, 6, 0.79, 14, 18]



In [64]:

    
lst1 = lst.copy()



In [65]:

    
id(lst1)









    Out[65]:





140508654127560



In [66]:

    
lst1[2] = 379



In [67]:

    
lst1









    Out[67]:





[2, 6, 379, 14, 18]



In [68]:

    
lst









    Out[68]:





[2, 6, 0.79, 14, 18]



In [69]:

    
lst1 = lst[:]



In [71]:

    
id(lst1)









    Out[71]:





140508713976456



In [73]:

    
lst is lst1









    Out[73]:





False



In [74]:

    
lst









    Out[74]:





[2, 6, 0.79, 14, 18]



In [75]:

    
list(map(lambda x: x * 2, lst))









    Out[75]:





[4, 12, 1.58, 28, 36]



In [76]:

    
lst = list(range(10))



In [77]:

    
lst.remove(2)



In [78]:

    
lst









    Out[78]:





[0, 1, 3, 4, 5, 6, 7, 8, 9]



In [79]:

    
#lst.remove(-1)

#---------------------------------------------------------------------------
#ValueError                                Traceback (most recent call last)
#<ipython-input-6-9cb22bf5b017> in <module>()
#----> 1 lst.remove(-1)
#
#ValueError: list.remove(x): x not in list



In [80]:

    
del lst # Deleting the whole list



In [82]:

    
#lst

#---------------------------------------------------------------------------
#NameError                                 Traceback (most recent call last)
#<ipython-input-11-12f54a96f644> in <module>()
#----> 1 lst
#
#NameError: name 'lst' is not defined



In [88]:

    
#lst = list(range(10))
#lst[len(lst)] = 'new_value'

#---------------------------------------------------------------------------
#IndexError                                Traceback (most recent call last)
#<ipython-input-87-c4d3abf378eb> in <module>()
#      1 lst = list(range(10))
#----> 2 lst[len(lst)] = 'new_value'
#
#IndexError: list assignment index out of range



In [90]:

    
lst = list(range(10))

lst[1:6] = ['a', 'b', 'c', 'd', 'e']
lst









    Out[90]:





[0, 'a', 'b', 'c', 'd', 'e', 6, 7, 8, 9]