Comportamento interessante de se observar

console.py

Python 2.7.6 (default, Mar 22 2014, 22:59:56) 
[GCC 4.8.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> class Foo(object):
...     x = 9
...     def __init__(self, x):
...         self.x = x
...     def bar(self, y):
...         return self.x + y
... 
>>> 
>>> foo = Foo(5)
>>> 
>>> 
>>> def bar(self, y):
...     return self.x + y
... 
>>> 
>>> class Foo(object):
...     x = 9
...     def __init__(self, x):
...         self.x = x
...     bar = bar
... 
>>> 
>>> foo = Foo(5)
>>> 
>>> print bar(foo, 4) == 9
True
>>> print bar(Foo, 0) == 9
True
>>> 
>>> print Foo.bar(foo, 4) == 9
True
>>> print Foo.bar(Foo, 0) == 9
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unbound method bar() must be called with Foo instance as first argument (got type instance instead)
>>> 
>>> 
>>> 
>>> 
>>> class Foo(object):
...     __cache = []
...     def __init__(self, x):
...         self.__cache.append(x)
...     def add(self, x):
...         self.__cache.append(x)
...         return self
... 
>>> 
>>> foo_1 = Foo(10)
>>> foo_1.__cache
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'Foo' object has no attribute '__cache'
>>> class Foo(object):
...     __cache = []
...     def __init__(self, x):
...         self.__cache.append(x)
...     def add(self, x):
...         self.__cache.append(x)
...         return self
...     def get(self):
...         return self.__cache
... 
>>> 
>>> 
>>> 
>>> 
>>> foo_1 = Foo(10)
>>> foo_1.get()
[10]
>>> 
>>> foo_1.add(5)
<__main__.Foo object at 0x7f15c99c2890>
>>> foo1_.get()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'foo1_' is not defined
>>> foo_1.get()
[10, 5]
>>> foo_1.add(6).add(8).get()
[10, 5, 6, 8]
>>> 
>>> 
>>> foo_1 = Foo(5)
>>> foo_1.get()
[10, 5, 6, 8, 5]
>>> 
>>> foo_1.get()
[10, 5, 6, 8, 5]
>>> foo_1 = None
>>> 
>>> foo_1
>>> foo_1 = Foo(5)
>>> foo_1.get()
[10, 5, 6, 8, 5, 5]
>>> 
>>> 
>>> class Foo(object):
...     x = []
...     def __init__(self, a):
...         self.x.append(a)
...     def add(self, a):
...         self.x.append(a)
...         return self
...     def get(self):
...         return self.x
... 
>>> 
>>> 
>>> 
>>> 
>>> foo = Foo(0)
>>> 
>>> foo.get()
[0]
>>> foo.add(3).add(4)
<__main__.Foo object at 0x7f15c99c2ad0>
>>> foo.get9)
  File "<stdin>", line 1
    foo.get9)
            ^
SyntaxError: invalid syntax
>>> foo.get()
[0, 3, 4]
>>> 
>>> 
>>> foo = Foo(8)
>>> foo.get9)
  File "<stdin>", line 1
    foo.get9)
            ^
SyntaxError: invalid syntax
>>> foo.get()
[0, 3, 4, 8]
>>> 
>>> 
>>> type(foo)
<class '__main__.Foo'>
>>> foo.add(2)
<__main__.Foo object at 0x7f15c99c2b90>
>>> 
>>> 
>>> 
>>> 
>>> del(foo)
>>> 
>>> foo
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'foo' is not defined
>>> foo = Foo(5)
>>> 
>>> foo.get()
[0, 3, 4, 8, 2, 5]
>>> 
>>> foo
<__main__.Foo object at 0x7f15c99c2bd0>
>>> 
>>> foo.get()
[0, 3, 4, 8, 2, 5]
>>> 
>>> 
>>> foo = Foo(6)
>>> foo
<__main__.Foo object at 0x7f15c99c2ad0>
>>> 
>>> foo.get()
[0, 3, 4, 8, 2, 5, 6]
>>> 
>>> 
>>> print cx
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'cx' is not defined
>>> print foo.x
[0, 3, 4, 8, 2, 5, 6]
>>> 
>>> 
>>> 
>>> class Foo(object):
...     x = []
...     def __init__(self):
...         self.x = []
...     def add(self, a):
...         self.x.append(a)
...         return self
...     def get(self):
...         return self.x
... 
>>> 
>>> 
>>> 
>>> t = Foo()
>>> t
<__main__.Foo object at 0x7f15c99c2d50>
>>> t.get(
... )
[]
>>> t.add(1).add(4).add(5)
<__main__.Foo object at 0x7f15c99c2d50>
>>> t.get()
[1, 4, 5]
>>> 
>>> 
>>> 
>>> a = Foo()
>>> a
<__main__.Foo object at 0x7f15c99c2e50>
>>> a.get()
[]
>>> a.add(4).add(2)
<__main__.Foo object at 0x7f15c99c2e50>
>>> a.get()
[4, 2]
>>> t.get()
[1, 4, 5]
>>>