Hi everyone!

I would like to create instances of a class containing a list that's empty by default; instead of later setting this list to the final full list I would like to successively add items to it. Here's a piece of sample code illustrating this:

#!/usr/bin/python

class test:
    def __init__(self, lst=[], intg=0):
        self.lista   = lst
        self.integer = intg

name_dict = {}
counter   = 0

for name in ('Anne', 'Leo', 'Suzy'):
    counter += 1

    name_dict[name] = test()
    name_dict[name].integer += 1
    name_dict[name].lista.append(counter)

    print name, name_dict[name].integer, name_dict[name].lista

When I ran the above program I expected to get

Anne 1 [1]
Leo 1 [2]
Suzy 1 [3]

as I assumed lista to always be initialised to an empty list.

What I got instead was this:

Anne 1 [1]
Leo 1 [1, 2]
Suzy 1 [1, 2, 3]

If I replace self.lista = lst by self.lista = [] it works fine, just like when I add the line name_dict[name].lista = [] to the for loop.

Why is it that the contents of the previous objects' lists are retained, yet their values of integer aren't? I am rather new to Python, so it would be great if someone could point out to me where my thoughts/assumptions have gone astray.

Thanks a lot in advance for your replies.