What am I doing wrong?

[Sybren Stuvel]

keithlackey enlightened us with:
>       def __init__(self, folders = []):        
>           self.folders = folders

Read all about this very common mistake at
http://docs.python.org/tut/node6.html#SECTION006710000000000000000

>       def add_folder(self, folder):
>           self.folders.append(tuple(folder))

The line above has a combination of spaces and tabs. Use either spaces
or tabs, but not both, to indent your code.

Sybren
-- 
The problem with the world is stupidity. Not saying there should be a
capital punishment for stupidity, but why don't we just take the
safety labels off of everything and let the problem solve itself? 
                                             Frank Zappa