Class/Global variables vs Instance Variables ... 



Class/Global variables are like CoW, only when the instances assign them values they have their own memory location allocated. For example in this case a.bar is assigned a value and hence it has different memory  location allocated, but the same is not the case with b.bar

>>> class Foo(object): 
        bar = None
>>> repr(Foo.bar)
'None'
>>> a = Foo()
>>> a.bar = 1
 >>> repr(Foo.bar)
'None'
>>> a.bar
1
>>> b = Foo()
>>> b.bar
>>> repr(b.bar)
'None'
>>> a.bar
1
>>> id(Foo.bar)
135796184
>>> id(a.bar)
151257264
>>> id(b.bar)
135796184

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