How do I assign a numerical value to each uppercase Letter?

Question

How do i assign a numerical value to each uppercase letter, and then use it later via string and then add up the values.

EG.

A = 1, B = 2, C = 3 (etc..)

string = 'ABC'

Then return the answer 6 (in this case).

Answer 1

base = ord('A') - 1
mystring = 'ABC'
print sum(ord(char) - base for char in mystring)