In [1]:

    

class Point:
    """Represents a point in 2-D space."""


    

In [2]:

    

Point


    

    
Out[2]:





__main__.Point

In [3]:

    

blank = Point()
blank


    

    
Out[3]:





<__main__.Point at 0x7f49502f3eb8>

In [4]:

    

blank.x = 3.0
blank.y = 4.0


    

In [5]:

    

dir(blank)


    

    
Out[5]:





['__class__',
 '__delattr__',
 '__dict__',
 '__dir__',
 '__doc__',
 '__eq__',
 '__format__',
 '__ge__',
 '__getattribute__',
 '__gt__',
 '__hash__',
 '__init__',
 '__init_subclass__',
 '__le__',
 '__lt__',
 '__module__',
 '__ne__',
 '__new__',
 '__reduce__',
 '__reduce_ex__',
 '__repr__',
 '__setattr__',
 '__sizeof__',
 '__str__',
 '__subclasshook__',
 '__weakref__',
 'x',
 'y']

In [6]:

    

def print_point(p: Point) -> None:
    print("({:g}, {:g})".format(p.x, p.y))

print_point(blank)


    

    




(3, 4)

In [7]:

    

class Rectangle:
    """Represents a rectangle.
    attributes: width, height, corner.
    """


    

In [8]:

    

box = Rectangle()
box.width = 100.0
box.height = 200.0
box.corner = Point()
box.corner.x = 0.0
box.corner.y = 0.0


    

In [9]:

    

def find_center(rect: Rectangle) -> Point:
    p = Point()
    p.x = rect.corner.x + rect.width/2
    p.y = rect.corner.y + rect.height/2
    return p


    

In [10]:

    

center = find_center(box)
print_point(center)


    

    




(50, 100)

In [11]:

    

def grow_rectangle(rect: Rectangle, dwidth: float, dheight: float) -> None:
    rect.width += dwidth
    rect.height += dheight


    

In [12]:

    

box.width, box.height


    

    
Out[12]:





(100.0, 200.0)

In [13]:

    

grow_rectangle(box, 50, 100)
box.width, box.height


    

    
Out[13]:





(150.0, 300.0)

In [14]:

    

def move_rectangle(rect: Rectangle, dx: float, dy: float) -> None:
    rect.corner.x += dx
    rect.corner.y += dy
    
print_point(box.corner)
move_rectangle(box, 100, 50)
print_point(box.corner)


    

    




(0, 0)
(100, 50)

In [15]:

    

p1 = Point()
p1.x = 3.0
p1.y = 4.0
import copy
p2 = copy.copy(p1)


    

In [16]:

    

print_point(p1)
print_point(p2)
print(p1 is p2)
print(p1 == p2) # behaves as `is` operator


    

    




(3, 4)
(3, 4)
False
False

In [17]:

    

box2 = copy.copy(box) # preserve references
print(box2 is box)
print(box2.corner == box.corner)


    

    




False
True

In [18]:

    

box3 = copy.deepcopy(box) # recursively copy anything
print(box3 is box)
print(box3.corner == box.corner)


    

    




False
False

In [19]:

    

p = Point()
p.x = 3
p.y = 4
#p.z
#---------------------------------------------------------------------------
#AttributeError                            Traceback (most recent call last)
#<ipython-input-19-9b05942bb1b6> in <module>()
#      2 p.x = 3
#      3 p.y = 4
#----> 4 p.z
#
#AttributeError: 'Point' object has no attribute 'z'


    

In [20]:

    

type(p)


    

    
Out[20]:





__main__.Point

In [21]:

    

isinstance(p, Point)


    

    
Out[21]:





True

In [22]:

    

print(hasattr(p, 'x'))
print(hasattr(p, 'y'))
print(hasattr(p, 'z'))


    

    




True
True
False

In [23]:

    

try:
    x = p.x
except AttributeError:
    x = 0

print(x)


    

    




3