gistfile1.txt

import string


def to_index(col):
    col = col.lower()
    assert len(col) > 0 and not \
        [l for l in col if l not in string.lowercase]
    index = 0
    for i in range(1, len(col) + 1):
        if i == 1:
            multiplier = 1
        else:
            multiplier = (i-1) * 26
        index += (string.lowercase.index(col[-i]) + 1) * multiplier
    return index

assert to_index('A') == 1
assert to_index('AA') == 27
assert to_index('Z') == 26
assert to_index('AB') == 28
try:
    to_index('3')
except AssertionError:
    pass
else:
    assert False, 'col 3 is undefined'
try:
    to_index('')
except AssertionError:
    pass
else: