Validating and calculating WPS PIN checksum

wps_checksum.py

# -*- coding: utf-8 -*-
def checksum(pin):
    '''
    Standard WPS checksum algorithm.
    @pin — A 7 digit pin to calculate the checksum for.
    Returns the checksum value.
    '''
    accum = 0
    while pin:
        accum += (3 * (pin % 10))
        pin = int(pin / 10)
        accum += (pin % 10)
        pin = int(pin / 10)
    return ((10 - accum % 10) % 10)


if __name__ == '__main__':
    while True:
        try:
            pin = input('7-digit WPS PIN: ')[:7]
            pin = int(pin)
        except ValueError:
            print('Invalid input')
            continue
        chs = checksum(pin)
        print(f'Checksum: {chs}\n8-digit PIN: {(str(pin) + str(chs)).zfill(8)}\n')