Python: binary to decimal

binary2decimal.py

#!/usr/bin/env python2
# -*- coding: utf-8 -*-

def bin2dec(binary_string):
    """ Convert binary string to decimal number """
    decimal = 0
    while binary_string:
        decimal = decimal * 2 + (ord(binary_string[0]) - ord('0'))
        binary_string = binary_string[1:]
    
    return decimal