Compute absolute identity (# matching sites) between sequence strings.

def identity_abs(aseq, bseq):
    """Compute absolute identity (# matching sites) between sequence strings."""
    assert len(aseq) == len(bseq)
    return sum(a == b
               for a, b in zip(aseq, bseq)
               if not (a in '-.' and b in '-.'))