elosort.py

import sys
from itertools import combinations
from collections import defaultdict
from random import shuffle


def pick_one():
    while True:
        foo = input('Which one? ').strip().lower()
        if foo == 'a':
            return (1, 0)
        if foo == 'b':
            return (0, 1)
        print('Invalid choice')


def expected(A, B):
    return 1 / (1 + 10 ** ((B - A) / 400))


def elo(old, exp, score, k=32):
    return old + k * (score - exp)


def main():
    if len(sys.argv) > 1:
        rows = sys.argv[1:]
    else:
        rows = filter(None, list(x.strip() for x in sys.stdin))
    rows = list(rows)

    scores = defaultdict(lambda: 1200)
    pairs = [(a, b) for (a, b) in combinations(rows, 2)]
    shuffle(pairs)

    for idx, (a, b) in enumerate(pairs):
        print('[{}/{}]'.format(idx + 1, len(pairs)))
        print('A - {}\nB - {}'.format(a, b))

        oldscore_a = scores[a]
        oldscore_b = scores[b]
        score_a, score_b = pick_one()

        scores[a] = elo(
            oldscore_a,
            expected(oldscore_a, oldscore_b),
            score_a)

        scores[b] = elo(
            oldscore_b,
            expected(oldscore_b, oldscore_a),
            score_b)

        print()

    print(' Final score '.center(80, '-'))
    score_items = sorted(
        scores.items(), key=lambda x: (x[1], x[0]), reverse=True)
    for name, score in score_items:
        print('{:6.0f}: {}'.format(score, name))


if __name__ == '__main__':
    main()