def col_frequencies(col, weights=None, gap_chars='<STR_LIT>'):
counts = col_counts(col, weights, gap_chars)<EOL>scale = <NUM_LIT:1.0> / sum(counts.values())<EOL>return dict((aa, cnt * scale) for aa, cnt in counts.iteritems())<EOL>
Frequencies of each residue type (totaling 1.0) in a single column.