[portland] Still Having List/Tuple Problems

[Dylan Reinhardt]

The setdefault method returns what the dictionary has at the specified
key... but *sets* the value of that key first if no such key is found.

Thus, for this expression...

my_dict.setdefault(key, [])

...the return is always the list at my_dict[key]    You can append to
this because it's always a list.

Hope that's helpful.

Dylan




On Thu, Apr 17, 2008 at 9:29 AM, Rich Shepard <rshepard at appl-ecosys.com> wrote:
> 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
>  > ...
>
>  Dylan,
>
>    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,
>
>
>
>  Rich
>
>  --
>  Richard B. Shepard, Ph.D.               |  Integrity            Credibility
>  Applied Ecosystem Services, Inc.        |            Innovation
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