Newbie lists question

[Gerhard Häring]

On Tue, 14 Aug 2001 01:07:34 +0200, Gerhard Häring wrote:
>On Mon, 13 Aug 2001 15:17:57 -0700, Wolfe Maykut <wolfe at spam.me.not> wrote:
>>    Hi.  I'm trying to create a list on the end of a dictionary.   I'd
>>like to have a single loop, but since the dictionary is dynamically
>>generated it appears as if I have to test to see if the key is around
>>and then treat each case differently in order to initialize the loop.
>>It looks ugly.  Is there a nicer way of doing this that I'm missing?

>>[...]
>>    # This is the loop I think is tres' ugly:
>>    if prefixes.has_key(prefix):   
>>       prefixes[prefix].append(file)
>>    else:
>>        prefixes[prefix] = []
>>        prefixes[prefix].append(file)
>
>I don't think this is ugly, it does even get quite nice when rewriting it:
>
>if not prefixes.has_key(prefix):
>    prefixes[prefix] = []
>prefixes[prefix].append(file)

Well, I found out it is possible to write this shorter with the setdefault()
method of the dictionary, but I find it also less readable:

prefixes[prefix] = prefixes.setdefault(prefix, []) + [file]

Gerhard
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