Appending a non-empty element to a non-empty list from
a dictionary results in a list of None


Scope:
Python 2.3.3 (#51, Dec 18 2003, 20:22:39) [MSC v.1200
32 bit (Intel)] on win32 and 
Python 2.3.4 (#53, May 25 2004, 21:17:02) [MSC v.1200
32 bit (Intel)] on win32
yield identical results.

Description:

The code (which is supposed to be used in a function
for deleting duplicate files...) contains this line:

print
"Warning!",(md5,len),'*',MainDic[(md5,len)],'*',name,'*',MainDic[(md5,len)].append(name)

which prints the following result:

Warning! ('5e011eda91336d21d3bfc5d5a686bb44\n', '7217')
*
['D:\\_Arbeit\\_In\\_Roaming\\_Telework\\www.ivc.ca\\part9.html',
'D:\\_Arbeit\\_I
n\\_Roaming\\_Telework\\www.ivc.ca\\part9.html.primary']
*
D:\_Arbeit\_In\_Roaming\_Telework\www.ivc.ca\part9.html.primary
* None

How can this be?

The tuple is not empty, the entry for it in the
dictionary exists, it is a list of strings, name is not
empty and a string, but appending name to the list from
the dictionary yields "None". Am I missing something,
or is this really a bug?

Logged In: YES 
user_id=896722

Ok, I missed something:

>>> x=['a']
>>> print x.append('b')
None
>>> print x
['a', 'b']

So this is not a bug.

Logged In: YES 
user_id=341410

I'll also mention that you are shadowing the global 'len'
and likely global 'md5' with your variable names.

Since you seem to be relatively new to Python, I'll just say
that such things are generally frowned upon in production
Python software, as it tends to confuse others who would
read your code.