converting letters to numbers

[kjakupak at gmail.com]

On Tuesday, October 8, 2013 11:36:51 AM UTC-4, rand... at fastmail.us wrote:
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> Your description says capital letters, but 'a' is a lowercase letter.
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> Does "mod 26" means A is 1, or is it 0? i.e., is A+A = B or is it A?
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> What should your function do if the letter isn't a capital letter from
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> the basic set of 26 English letters?

A is 0. 

Transfer it to an uppercase letter if it's a letter, if it's not then an error.
This isn't right, I know, just testing around

def add(c1, c2):
    ans = ''
    for i in c1 + c2:
        ans += chr((((ord(i)-65))%26) + 65)
    return ans