I want to make a list of strings, replacing the each of the letters in Amino to all of the strings in the list within the following dictionary items: Amino = "mvkhdlsr" dct = { 'f' : ['UUU', 'UUC'], 'l' : ['UUA', 'UUG', 'CUU', 'CUG', 'CUA', 'CUG'], 'i' : ['AUU', 'AUC', 'AUA'], 'm' : ['AUG'], 'v' : ['GUU', 'GUC', 'GUA', 'GUG'], 's' : ['UCU', 'UCC', 'UCA', 'UCG', 'AGU', 'AGC'], 'p' : ['CCU', 'CCC', 'CCA', 'CCG'], 't' : ['ACU', 'ACC', 'ACA', 'ACG'], 'a' : ['GCU', 'GCC', 'GCA', 'GCG'], 'y' : ['UAU', 'UAC'], 'x' : ['UAA', 'UAG', 'UGA'], 'h' : ['CAU', 'CAC'], 'q' : ['CAA', 'CAG'], 'n' : ['AAU', 'AAC'], 'k' : ['AAA', 'AAG'], 'd' : ['GAU', 'GAC'], 'e' : ['GAA', 'GAG'], 'c' : ['UGU', 'UGC'], 'w' : ['UGG'], 'r' : ['CGU', 'CGC', 'CGA', 'CGG', 'AGA', 'AGG'], 'g' : ['GGU', 'GGC', 'GGA', 'GGG'] } For example, if Amino is "mfy", the desired output is AUGUUUUAU AUGUUUUAC AUGUUCUAU AUGUUCUAC since m has only one case (AUG), f has two cases (UUU, UUC), and y also has two cases (UAU, UAC). I've tried something like for word in Amino.split(): if word in dict: for key, value in dict.items(): for i in (0,len(value) - 1): for idx in value: (unfinished code) but could not figure it out. Continue reading...