Naive string entropy calculator

entropy

#!/usr/bin/env python3

import os
import fileinput
import string
import math


def get_string():
    return fileinput.input()[0]


pools = [string.ascii_lowercase, string.ascii_uppercase, string.digits, string.punctuation, " "]


def entropy(s):
    member_pools = filter(lambda pool: has_members(s, pool), pools)
    pool_size= sum(map(lambda pool: len(pool), member_pools))

    return len(s) * lg(pool_size)


def lg(x):
    return math.log(x) / math.log(2)


def has_members(s, chars):
    for c in s:
        if c in chars:
            return True
    return False


def main():
    s = get_string()
    print(entropy(s))


if __name__ == "__main__":
    main()