RosettaCode_validateISIN created by tapicella - https://repl.it/HnEm/27

RosettaCode_validateISIN.py

'''
An International Securities Identification Number (ISIN) is a unique international identifier for a financial security such as a stock or bond. 

 Replace letters with digits, by converting each character from base 36 to base 10, e.g. AU0000XVGZA3 →1030000033311635103.
Perform the Luhn test on this base-10 number.

US0378331005:TRUE
US0373831005:FALSE
U50378331005:FALSE
AU0000XVGZA3:TRUE
AU0000VXGZA3:TRUE
FR0000988040:TRUE
US03378331005: FALSE

Luhn test: 

    Reverse the order of the digits in the number.
    Take the first, third, ... and every other odd digit in the reversed digits and sum them to form the partial sum s1
    Taking the second, fourth ... and every other even digit in the reversed digits:

        Multiply each digit by two and sum the digits if the answer is greater than nine to form partial sums for the even digits
        Sum the partial sums of the even digits to form s2

    If s1 + s2 ends in zero then the original number is in the form of a valid credit card number as verified by the Luhn test.
    
    49927398716       TRUE
    49927398717       FALSE
    1234567812345678  FALSE
    1234567812345670  TRUE

http://rosettacode.org/wiki/Luhn_test_of_credit_card_numbers
http://rosettacode.org/wiki/Validate_International_Securities_Identification_Number
'''
import functools, string 

def ps(n):
  return (n//10)+(n%10)

def LuhnTest(n):
  s_n = str(n)[::-1]
  odds = s_n[0::2]
  evens = s_n[1::2]
  s1 = 0 
  s2 = 0 
  for o in odds:
    s1 += int(o) 
  for e in evens:
    s2 += ps(2*int(e))
  return((s1+s2)%10 == 0)
  
def validate(n):
  if len(n) != 12:
    return False
  alpha = list(string.ascii_uppercase)
  if n[0] not in alpha or n[1] not in alpha or n[11] in alpha:
    return False
  base10 = ""
  for c in n: 
    if c in alpha:
      base10 += str(10+alpha.index(c))
    else:
      base10 += c
  return LuhnTest(base10)
       
print(validate("US0378331005"))
print(validate("US0373831005"))
print(validate("U50378331005"))
print(validate("AU0000XVGZA3"))
print(validate("AU0000VXGZA3"))
print(validate("FR0000988040"))
print(validate("FR000098804O"))
print(validate("US03378331005"))