Newbie look at Python and OO

[Bruno Desthuilliers]

walterbyrd a écrit :
> Thanx for all the replies, I may be slowly getting it. But, can
> anybody explain this?
> 
> 
>>>>a = 'hello'
>>>>b = 'hello'
>>>>a is b
> 
> True
> 
>>>>a = 'hello there'
>>>>b = 'hello there'
>>>>a is b
> 
> False
> 
Python - well, CPython (the reference C implementation) at least - tries 
to optimize memory usage by "interning" (caching/reusing) string objects 
when possible. You'll find a similar behaviour with integers:
 >>> a = 5
 >>> b = 5
 >>> a is b
True
 >>> a = 50000
 >>> b = 50000
 >>> a is b
False
 >>>

IOW, this is an implementation detail. FWIW, you should not use identity 
tests on immutable objects (the None object set aside) - since they are 
immutable, equality test is enough.