Question

For class A, why is aMap member variable being shared between object and object b?

>>> class A:
...     aMap = {}

>>> a = A()
>>> a.aMap["hello"] = 1

>>> b = A()
>>> b.aMap["world"] = 2

>>> c = []
>>> c.append(a)
>>> c.append(b)

>>> for i in c:
...     for j in i.aMap.items():
...         print j
('world', 2)  
('hello', 1)  
('world', 2)  
('hello', 1)  

Answer 1

Because you defined it as a class attribute, not instance attribute.

If you wish to have it as instance attribute and not be shared between instances, you have to define it like this:

class A(object):
    def __init__(self):
        self.aMap = {}