indexing lists/arrays question

[Carey Tilden]

On Thu, May 13, 2010 at 8:45 AM, a <oxfordenergyservices at googlemail.com> wrote:
> On 13 May, 16:19, Tim Chase <python.l... at tim.thechases.com> wrote:
>> On 05/13/2010 09:36 AM, a wrote:
>>
>> > this must be easy but its taken me a couple of hours already
>>
>> > i have
>>
>> > a=[2,3,3,4,5,6]
>>
>> > i want to know the indices where a==3 (ie 1 and 2)
>>
>> indexes = [i for (i, v) in enumerate(a) where v==3]
>>
>> > then i want to reference these in a
>>
>> In a _what_?  You can then do things like
>>
>>    for i in indexes:
>>      print a[i]
>>
>> (but you already know these are "3", so it's not very exciting...)
>>
>> -tkc
>
> really its to get the indexes in 1 array where something equals
> something then reference these in another array.
> --
> http://mail.python.org/mailman/listinfo/python-list
>

Out of curiosity, why are you using two arrays?  Have you considered a
dict?  There are of course good reasons not to use a dict in this
situation, but you haven't said one way or another.

Carey