Matching codons

So I'm now learning about nested pools and I don't really get it. my task is to return all matching pairs in following format:

[('AAG', 'TTC'), ('GAT', 'CTA'), ('TTG', 'AAC'), ('CAT', 'GTA'), ('GGC', 'CCG'), ('ATT', 'TAA'), ('TCT', 'AGA')]

so this is my code:

def matching_codons(complements, poolA, poolB):
complements = {'A':'T', 'C':'G', 'T':'A', 'G':'C'}
poolA = ['AAG', 'TAC', 'CGG', 'GAT', 'TTG', 'GTG', 'CAT', 'GGC', 'ATT', 'TCT']
poolB = ['TAA', 'CTA', 'AAC', 'TTC', 'AGA', 'CCC', 'CCG', 'GTA']
final = []
 for i in poolA:
  for z in poolB:
    if i and z in complements:
      final.append()
      return(final)

It's not working and I don't know why, I don't quite get it. How can I make a statement so that the poolA and the poolB will match according to the dictionary provided?

Solution

Try to search for the complements in the other pool, instead of walking through every elements in poolA and poolB.

def _complements(complements, str):
    return ''.join([complements[i] for i in str])

def matching_codons(complements, poolA, poolB):
    final = []
    for i in poolA:
        if _complements(complements, i) in poolB:
            final.append((i, _complements(complements, i)))
    return final
complements = {'A':'T', 'C':'G', 'T':'A', 'G':'C'}
poolA = ['AAG', 'TAC', 'CGG', 'GAT', 'TTG', 'GTG', 'CAT', 'GGC', 'ATT', 'TCT']
poolB = ['TAA', 'CTA', 'AAC', 'TTC', 'AGA', 'CCC', 'CCG', 'GTA']
print matching_codons(complements, poolA, poolB)

output

[('AAG', 'TTC'), ('GAT', 'CTA'), ('TTG', 'AAC'), ('CAT', 'GTA'), ('GGC', 'CCG'), ('ATT', 'TAA'), ('TCT', 'AGA')]