def calc_pid(seq1, seq2):
    """
    Calculates the percentage ID (still as a decimal)
    between two sequences.

    Parameters
    ----------
    seq1: str
    seq2: str

    Returns
    -------
    pid: float
    """
    alnlen = len(seq1)
    identical = 0
    for i in range(0, len(seq1)):
        if seq1[i].isalpha() and seq2[i].isalpha() and seq1[i] == seq2[i]:
            identical += 1
    pid = identical/alnlen
    return pid