nested looping

[andrew cooke]

bit late here, but if it's as simple as you say, i think it would be much
more efficient (because you only scan checklist and alist once each) to
do:

known = set()
for check in checklist:
  known.add(check[0:-1])
missing = filter(lambda alpha: alpha not in known, alist)

andrew


PK wrote:
> Excellent! Thanks all. Since I need to have this running on python 2.4 as
> well, I think I'll choose,
>
> for alpha in alist:
>    for xy in xlist:
>         if alpha+xy in checklist:
>            break
>    else:
>        missing.append(alpha)
>
> jus tested and worked like a charm.
>
> Appreciate your help!!
>
>
>
> On Wed, Apr 8, 2009 at 6:12 PM, Luis Alberto Zarrabeitia Gomez
> <kyrie at uh.cu>wrote:
>
>>
>> Quoting PK <superprad at gmail.com>:
>>
>> > So I'm trying to see whats the cleanest way to do this:
>> >
>> > I have a
>> >
>> > checklist = [ax, bx, by, cy  ..] (a combination of a,b,c with x and y,
>> > either both on one)
>> >
>> > allist = [a,b,c,....]
>> > xlist = [x, y, ..]
>> >
>> [...]
>> > now the problem is I want to include alpha in missing list only if
>> > none of the combinations from xlist with alpha are in checklist.
>>
>> This is untested:
>>
>> for alpha in alist:
>>    for xy in xlist:
>>         if alpha+xy in checklist:
>>            break
>>    else:
>>        missing.append(alpha)
>>
>> (note that the "else" is for the "for", not the "if")
>>
>> You could also try the any/all functions from python2.5:
>>
>> for alpha in alist:
>>    if not any(alpha + xy in checklist for xy in xlist):
>>        missing.append(alpha)
>>
>>
>> Or the really not recommended one-liner:
>>
>> missing = [alpha for alpha in alist if not any(alpha + xy in checklist
>> for
>> xy in
>> xlist)]
>>
>> (remember, all of this is untested)
>>
>> --
>> Luis Zarrabeitia
>> Facultad de Matemática y Computación, UH
>> http://profesores.matcom.uh.cu/~kyrie<http://profesores.matcom.uh.cu/%7Ekyrie>
>>
>>
>> --
>> Participe en Universidad 2010, del 8 al 12 de febrero de 2010
>> La Habana, Cuba
>> http://www.universidad2010.cu
>>
>>
> --
> http://mail.python.org/mailman/listinfo/python-list
>