Converts spreadsheet-style column names (A, B, AA, etc) of any length into an integer index, such that A==0, B==1, AA==26, etc. Use upper or lower case.

spreadsheet-col-index.py

def col(letters):
    """ Convert column letters into zero-indexed number """
    letters = letters.lower()
    num = 0
    for l in letters[:-1]:
        num += (ord(l) - 96) * 26
    num += (ord(letters[-1]) - 96)
    return num - 1