Convert an excel or spreadsheet column letter to its number in Pythonic fashion

Question

Is there a more pythonic way of converting excel-style columns to numbers (starting with 1)?

Working code up to two letters:

Answer 1

Here's what I use (wrote before I found this page):

def col_to_index(col):
    return sum((ord(c) - 64) * 26**i for i, c in enumerate(reversed(col))) - 1

And some runs:

>>> col_to_index('A')
1
>>> col_to_index('AB')
28
>>> col_to_index('ABCD')
19010