A Python solution to the 2009 Google Code Jam problem entitled Alien Numbers

AlienNumbers.py

import sys
import re
"""
http://code.google.com/codejam/contest/32003/dashboard#s=p0
"""


def process(current_case):
    alien_number, source_language, target_language = current_case.split()
    source_language = list(source_language)
    target_language = list(target_language)

    decimal_value = 0
    for index, numeral in enumerate(reversed(alien_number)):
        # add the following to the current decimal value
        #  the position of the symbol in the source language (its value)
        #  multiplied by the number of symbols used by the language (its base)
        #  to the power of the position it was found in the alien_number (its magnitude)
        decimal_value += source_language.index(numeral)*len(source_language)**index

    target_number = ''
    while decimal_value:
        target_number = target_language[decimal_value % len(target_language)] + target_number
        decimal_value /= len(target_language)
    return target_number

if __name__ == "__main__":
    filename = sys.argv[1]
    cases = open(filename).read().splitlines()
    cases.pop(0)                                            # discard the first line of input
    output = re.split('\.', filename)[0] + '-out.txt'       # generate output file
    f_out = open(output, 'w')
    for n, case in enumerate(cases):
        result = 'Case #' + str(n+1) + ': ' + process(case)
        f_out.write(result + '\n')
        print result
    print 'Results saved to '+output