Huffman coding algorithm.py

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

def encode(symb2freq):    
    heap = [[wt,[sym," "]] for sym, wt in symb2freq.items()]
    heapify(heap)
    while len(heap)>1:
        lo=heappop(heap)
        hi=heappop(heap)
        for pair in lo[1:]:
            pair[1]='0' + pair[1]
        for pair in hi[1:]:
            pair[1]='1' + pair[1]
        heappush(heap,[lo[0]+ hi[0]]+lo[1:]+hi[1:])
    return sorted(heappop(heap)[1:],key=lambda p:(len(p[-1]),p))

txt= "this is an example for huffman encoding"
symb2freq = defaultdict(int)
for ch in txt:
    symb2freq[ch] += 1
    #in Python 3.1+:
    #symb2freq= collections.Counter(txt)
    huff = encode(symb2freq)
print("Symbol\tWeight\tHuffman Code")
for  p in huff:
    print("%s\t%s\t%s"%(p[0],symb2freq[p[0]],p[1]))