Huffman code with python

huffman.py

from collections import Counter
import heapq

class Node(object):
    def __init__(self, pairs, frequency):
        self.pairs = pairs
        self.frequency = frequency

    def __repr__(self):
        return repr(self.pairs) + ", " + repr(self.frequency)

    def merge(self, other):
        total_frequency = self.frequency + other.frequency
        for p in self.pairs:
            p[1] = "1" + p[1]
        for p in other.pairs:
            p[1] = "0" + p[1]
        new_pairs = self.pairs + other.pairs
        return Node(new_pairs, total_frequency)

    def __lt__(self, other):
        return self.frequency < other.frequency

def huffman_codes(s):
    table = [Node([[ch, '']], freq) for ch, freq in Counter(s).items()]
    heapq.heapify(table)
    while len(table) > 1:
        first_node = heapq.heappop(table)
        second_node = heapq.heappop(table)
        new_node = first_node.merge(second_node)
        heapq.heappush(table, new_node)
    return dict(table[0].pairs)

print(huffman_codes('yashaswita'))