gather information from various files efficiently

Fernando Perez fperez528 at yahoo.com
Tue Dec 14 12:01:36 CET 2004


Keith Dart wrote:

> Aye...
> 
> the dict.keys() line creates a temporary list, and then the 'in' does a
> linear search of the list. Better would be:
> 
> try:
>      dict[a].append(b)
> except KeyError:
>      dict[a] = [b]
> 
> since you expect the key to be there most of the time, this method is
> most efficient. You optomistically get the dictionary entry, and on the
> exceptional case where it doesn't yet exist you add it.

I wonder if

dct.setdefault(a,[]).append(b)

wouldn't be even faster.  It saves setting up the try/except frame handling in
python (I assume the C implementation of dicts achieves similar results with
much less overhead).

Cheers,

f

ps.  I changed dict->dct because it's a generally Bad Idea (TM) to name local
variables as builtin types.  This, for the benefit of the OP (I know you were
just following his code conventions).




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