Approximate time to brute-force a password

howlong.py

"""Calculates how long a password might take to brute force
"""

def chunks(l, n):
    for i in xrange(0, len(l), n):
        yield l[i:i+n]

def human_readable_number(n):
    return ",".join(list(chunks(str(n)[::-1],3)))[::-1]

def time(total, persecond):
    ttlsec = total / float(persecond)
    minutes = ttlsec/60.0
    hours = minutes/60.0
    days = hours/24.0
    weeks = days/7.0
    years = weeks/52
    return int(round(years))

def main():
    num_possible_characters = (26 + 26 + 12)
    password_size = 20
    hashes_per_second = 1000000
    number_of_machines = 500

    permus = num_possible_characters ** password_size

    print human_readable_number(permus)

    howlong = time(permus, hashes_per_second * number_of_machines)

    print human_readable_number(howlong) + " years"

if __name__ == '__main__':
    main()