[portland] Still Having List/Tuple Problems

Rich Shepard rshepard at appl-ecosys.com
Thu Apr 17 18:29:42 CEST 2008

On Wed, 16 Apr 2008, Dylan Reinhardt wrote:

>>>> grouper = {}
>>>> for left, right in my_tuples:
> ...         grouper.setdefault(left, []).append(right)
> now you have a dict with values groped by keys, as shown below...
>>>> for key in grouper.keys():
> ...        print key
> ...        for value in grouper[key]:
> ...             print '\t%s' % value
> ...


   Works perfectly for my report.

   I read in 'Python in a Nutshell' about the setdefault() method for
dictionaries, but see nothing about extending that with .append(). Is this a
short cut to adding the rightside values to each of the keys?

Thanks for the lesson,


Richard B. Shepard, Ph.D.               |  Integrity            Credibility
Applied Ecosystem Services, Inc.        |            Innovation
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