Buildin a Peptide Sequence From Hand
There are two methods in PyMol for building a peptide sequence from hand. First, you may simply hold down the alt (option on Mac) key and type in the one-letter code for the sequence. Secondly, you can write a script like the following
for aa in "DCAHWLGELVWCT": cmd._alt(string.lower(aa))
which will build the amino acid sequence "DCAHWLGELVWCT".