[Tutor] List index usage: is there a more pythonesque way?

[C M Caine]

> Something is wrong in the following if statement, as both paths execute the
> same code.
>
>>             if spaceDict['1st'+key] == 0:
>>                 spaceDict['nth'+key] = i
>>             else:
>>                 spaceDict['nth'+key] = i
>>         for form in forms:
>>             adjustedSpaceDict[form] = spaceDict['nth'+form] - \
>>                                       spaceDict['1st'+form]
>>         return (numDict, adjustedSpaceDict)


Oh yeah, I think I pulled up an old version of the source file by
accident, I've fixed that bug already.
The correct code is:

# stuff...
             if spaceDict['1st'+key] == 0:
                 spaceDict['1st'+key] = i
             else:
                 spaceDict['nth'+key] = i
         for form in forms:
             adjustedSpaceDict[form] = spaceDict['nth'+form] - \
                                       spaceDict['1st'+form]
         return (numDict, adjustedSpaceDict)

I don't think I'll use defaultdict here, though thanks for pointing it
out to me, that's the first time I've heard of it; I'm trying to keep
the number of outside modules to a minimum as this is an assessed
piece of work.

Thanks, Bob.


On 19 April 2010 00:34, bob gailer <bgailer at gmail.com> wrote:
> On 4/18/2010 6:53 PM, C M Caine wrote:
>>
>> # Example data for forms and timetable:
>> forms = ["P7", "P8", "P9", "P10", "P11", "S7", "S8", "S9", "S10",
>> "S11", "IMA", "CAT", "FOR", "RLS", "EMPTY"]
>>
>> timetable = ['CAT', 'P10', 'P8', 'EMPTY', 'EMPTY', 'EMPTY', 'S10',
>> 'S8', 'IMA', 'EMPTY', 'S7', 'S10', 'P9', 'EMPTY', 'EMPTY', 'EMPTY',
>> 'S7', 'EMPTY', 'EMPTY', 'RLS', 'FOR', 'EMPTY', 'EMPTY', 'EMPTY', 'S9',
>> 'EMPTY', 'EMPTY', 'EMPTY', 'EMPTY', 'EMPTY', 'EMPTY', 'EMPTY',
>> 'EMPTY', 'EMPTY', 'S8', 'IMA', 'S11', 'P8', 'EMPTY', 'IMA', 'EMPTY',
>> 'EMPTY', 'S11', 'S11', 'EMPTY', 'EMPTY', 'EMPTY', 'P7', 'S9', 'P11',
>> 'P11', 'EMPTY', 'EMPTY', 'EMPTY', 'EMPTY', 'EMPTY', 'EMPTY', 'EMPTY',
>> 'EMPTY', 'EMPTY', 'P9', 'EMPTY', 'EMPTY', 'P8', 'FOR', 'S10', 'S11',
>> 'S7', 'P7', 'EMPTY', 'EMPTY', 'IMA', 'EMPTY', 'S9', 'P10', 'P11',
>> 'CAT', 'S8', 'P9', 'RLS']
>>
>> def analyseTimetable():
>>         "Find number of and spaces between each form."
>>
>
> Consider using defaultdict in the collections module. The first time a key
> is referenced it is automatically added with a specified value.
>
>
> import collections
>         numDict = collections.defaultdict(0)
>         spaceDict = collections.defaultdict(0)
>
>>         adjustedSpaceDict = {}
>>
>
> If you use enumerate then you can replace timetable[i] with key
>>
>>         for i, key in enumerate(timetable):
>>             numDict[key] += 1
>>
>
> Something is wrong in the following if statement, as both paths execute the
> same code.
>
>>             if spaceDict['1st'+key] == 0:
>>                 spaceDict['nth'+key] = i
>>             else:
>>                 spaceDict['nth'+key] = i
>>         for form in forms:
>>             adjustedSpaceDict[form] = spaceDict['nth'+form] - \
>>                                       spaceDict['1st'+form]
>>         return (numDict, adjustedSpaceDict)
>>
>> # End example
>>
>> This function works fine, but I think that using range(len(timetable))
>> is clumsy. On the other hand, I need the indexes to track the number
>> of spaces between instances of each form. Without using another loop
>> (so not using list.index), is there a way of getting the index of the
>> list entries?
>
>
> --
> Bob Gailer
> 919-636-4239
> Chapel Hill NC
>
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