Py3

huffman.py

from collections import Counter
from heapq import heapify, heappop, heappush

s = input()
c = Counter(s)
pq = [(c[k], k, None, None) for k in c]
codes = {}
heapify(pq)
while len(pq) > 1:
    r = heappop(pq)
    l = heappop(pq)
    heappush(pq, (l[0] + r[0], l[1] + r[1], l, r))


def buildCodes(parent, code):
    if parent:
        if len(parent[1]) == 1:
            codes[parent[1]] = code
        buildCodes(parent[2], code + '0')
        buildCodes(parent[3], code + '1')


buildCodes(pq[0], '')
print(codes)