[Tutor] efficient method to search between two lists

[Srinivas Iyyer]

Thank you Terry, 
  I learned some stuff from your snippet. I used 'Set'
but never got to use its power using LC. 

Thanks again
Srini



--- Terry Carroll <carroll at tjc.com> wrote:

> On Wed, 22 Mar 2006, Srinivas Iyyer wrote:
> 
> > I cannot think of any other smart method since
> these
> > are the only two ways I know possible. 
> > 
> > Would any one please help me suggesting a neat and
> > efficient way.  
> 
> I'm thinking:
> 
> 1) use sets to get subsets of both lists down to
> only those elements that 
> will match at least one element in another list; 
> 
> 2) loop and compare, but only on those elements you
> know will match 
> somewhere (because of step #1)
> 
> One try:
> 
> list_a = ['S83513\tNM_001117', 'X60435\tNM_001117',
> 'U75370\tNM_005035', 'U05861\tNM_001353',
> 'S68290\tNM_001353', 'D86864\tNM_145349',
> 'D86864\tNM_003693', 'D86864\tNM_145351',
> 'D63483\tNM_145349', 'D63483\tNM_003693',
> 'D63483\tNM_145351', 'S66427\tNM_002892',
> 'S57153\tNM_002892']
> 
> list_b = ['HC_G110\t1000_at\tS83513',
> 'HC_G110\t1001_at\tD63483',
> 'HC_G110\t1002_f_at\tD86864',
> 'HC_G112\t1003_s_at\tX60435',
> 'HC_G112\t1004_at\tS57153']
> 
> set_a =  set([(x.split('\t'))[0] for x in list_a])
> set_b =  set([(x.split('\t'))[2] for x in list_b])
> intersection = list(set_a & set_b)
> 
> for (whole_b, keypart_b) in \
>     [(x, x.split('\t')[2]) for x in list_b
>      if x.split('\t')[2] in intersection]:
>     
>     for (whole_a, keypart_a) in \
>         [(x, x.split('\t')[0]) for x in list_a
>         if x.split('\t')[0] in intersection]:
>         
>         if keypart_b == keypart_a:
>             print whole_b+whole_a
> 
> Gives as output:
> 
> HC_G110 1000_at S83513S83513    NM_001117
> HC_G110 1001_at D63483D63483    NM_145349
> HC_G110 1001_at D63483D63483    NM_003693
> HC_G110 1001_at D63483D63483    NM_145351
> HC_G110 1002_f_at       D86864D86864    NM_145349
> HC_G110 1002_f_at       D86864D86864    NM_003693
> HC_G110 1002_f_at       D86864D86864    NM_145351
> HC_G112 1003_s_at       X60435X60435    NM_001117
> HC_G112 1004_at S57153S57153    NM_002892
> 
> 
> (Note, my tab settings are different from yours,
> hence the different 
> output.)
> 
> _______________________________________________
> Tutor maillist  -  Tutor at python.org
> http://mail.python.org/mailman/listinfo/tutor
> 


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