Generate all possible string from two strings keeping position in python

Question

Given two words:

AT
TC

I want to generate all possible combinations (not sure if combination applies here) that can be produced by replacing one by one character of those two strings, as a result:

AT
TT
AC
TC

Edit:

I've tried:

from itertools import product
ref = "ACGT"
snp = "TGCA"
prod = product(ref,snp)
for p in prod:
    print p

but the result is:

('A', 'T')
('A', 'G')
('A', 'C')
('A', 'A')
('C', 'T')
('C', 'G')
('C', 'C')
('C', 'A')
('G', 'T')
('G', 'G')
('G', 'C')
('G', 'A')
('T', 'T')
('T', 'G')
('T', 'C')
('T', 'A')

Not what I'm looking for. I'm expecting something like (each result should be same lenght as input):

ACGT
TCGT
AGGT
ACGA
....

Answer 1

You are looking for the itertools.product which you may use like:

>>> from itertools import product
>>> my_list = [ 'AT' , 'TC']

>>> list(product(*my_list))
[('A', 'T'), ('A', 'C'), ('T', 'T'), ('T', 'C')]

To get these values as string, you may use a list comprehension as:

>>> [''.join(s) for s in product(*my_list)]
['AT', 'AC', 'TT', 'TC']

Edit (Based on the edit in the question)

For the new example you shared , you should be using zip with the above list comprehension expression and itertools.product as:

>>> ref = "ACGT"
>>> snp = "TGCA"

>>> [''.join(s) for s in product(*zip(ref,snp))]
['ACGT', 'ACGA', 'ACCT', 'ACCA', 'AGGT', 'AGGA', 'AGCT', 'AGCA', 'TCGT', 'TCGA', 'TCCT', 'TCCA', 'TGGT', 'TGGA', 'TGCT', 'TGCA']