How do you access a list in group of 3 in python? [duplicate]

Answer 1

With a nod to Óscar, who figured out the bulk of the problem, I think the OP is asking about something like this:

codon = 'AACTGCAGCTCA'

list = [codon[i:i+3] for i in range(0, len(codon), 3)]

=> ['AAC', 'TGC', 'AGC', 'TCA']

The list ['AAC', 'ACT', 'CTG', 'TGC', 'GCA', 'CAG', 'AGC', 'GCT', 'CTC', 'TCA'] was an unintended result of the OP's code, because each triplet contains the last two characters of the previous one.

Edit: Also, this chunk of code:

for p in patCodon:
    for d in dna:
        if d == p:
             x = dna[p]
             print (p)
             patCode.append(x)

should probably be this instead:

for p in patCodon:
    if p in dna:
        x = dna[p]
        print (p)
        patCode.append(p)

The reason is that checking for membership with in is much faster than looping over the members.

This will only work if dna is a dict. If dna is a list, the same syntax will work to check whether p is in dna, but x = dna[p] is probably a mistake.