Variable Modifications in a class

[Sean Ross]

"Mehta, Anish" <Anish.Mehta at enst-bretagne.fr> wrote in message
news:mailman.1054658001.11458.python-list at python.org...
>    c = b

The problem is with this line. c = b makes c an alias for b, so that when
you change the value of c's attributes, you are changing the values for b's
attributes. So, when you later say

>    c.a = 30
>    c.b = 40

This is *roughly* equivalent to the following:

b.a = c.a = 30
b.b = c.b = 40

You see, earlier, when you created b and c with:
b = ab()
c = ab()

you bind two seperate instances of the class ab (which aliases class AB, in
your example). But, when you later *re-bind* c to b, there are no longer
referrers to two seperate instances, c and b are now bound to the same
instance. To see this, put:

print c is b

after

b = ab()
c = ab()

then put it after

c = b

an notice the results.