python - Changing multiple positions in a list -

i have string want manipulate @ every position throughout it's length.

for example, have string looks this:

string1 = 'aatgcatt' 

i want create list change 1 position @ time either a, t, c, or g. thinking of using approach so:

liststring = list(string1) changedstrings = [] pos in range(2, len(liststring) - 2): ##i don't want change first , last characters of string     if liststring[pos] != 'a':         liststring[pos] = 'a'         random1 = "".join(liststring)         changedstrings.append(random1) 

i thinking of using similar approach append rest of changes (changing rest of positions g,c, , t) list generated above. however, when print changedstrings list, appears code changes of positions after first two. wanted change position 3 'a' , append list. change position 4 'a' , append list , on give me list so:

changedstrings = ['aaagcatt', 'aatacatt', 'aatgaatt']  

any suggestions?

you re-using old liststring variable. initialize inside loop instead:

changedstrings = [] pos in range(2, len(liststring) - 2):     liststring = list(string1)  # move line here     if liststring[pos] != 'a':         liststring[pos] = 'a'         random1 = "".join(liststring)         changedstrings.append(random1) print(changedstrings) 

results in

['aaagcatt', 'aatacatt', 'aatgaatt']