Newbie question about Class

[Gabriel Genellina]

En Tue, 13 Feb 2007 03:56:21 -0300, <JStoneGT at aol.com> escribió:

> I'm reading the book of "Dive into Python" and got these code pieces:
> class  UserDict:
> def __init__(self,  dict=None):              self.data = {}
> if dict is not None: self.update(dict)
> My question is,for the statement of:
> if dict is not None: self.update(dict)
> Why it's not this one below?
> if dict is not None: self.data.update(dict)
> Thanks.

The idea behind that class is to act "as-if" it were a real dictionary.  
Dicts have an update method, and UserDict should too. But it's not listed  
in the book (should appear a few lines below that code); this is a  
possible implementation:

def update(self, other):
     for key in other.keys():
         self.data[key] = other[key]

Given this method, __init__ works fine.
Using self.data.update(dict) is OK if the dict argument is a real  
dictionary, but not if it's another UserDict.

-- 
Gabriel Genellina