confused with local variables being retained

[Dan Brown]

Hi there,

I'm being confused (I guess) by namespace or scoping rules in Python; I
don't quite know why this piece of code is having the effect that it is:

class simple:
    def __init__ (self, label = 'spam'):
        self.label = label;

    def display (self, stufflist = []):
        stufflist.append (self.label)
        print stufflist

When I run the "display" method, this happens:

>>> B = simple ('B')
>>> B.display()
['B']
>>> B.display()
['B', 'B']
>>> B.display()
['B', 'B', 'B']

Why is the stufflist variable staying active from iteration to
iteration?  When I use non-lists, it seems to go away.

Thanks much,

-dan brown
 danb at alum.mit.edu