import sys class Letter: def __init__(self, letter, freq): self.letter = letter self.freq = freq self.bitstring = {} def __repr__(self): return f"{self.letter}:{self.freq}" class TreeNode: def __init__(self, freq, left, right): self.freq = freq self.left = left self.right = right def parse_file(file_path): """ Read the file and build a dict of all letters and their frequencies, then convert the dict into a list of Letters. """ chars = {} with open(file_path) as f: while True: c = f.read(1) if not c: break chars[c] = chars[c] + 1 if c in chars.keys() else 1 return sorted((Letter(c, f) for c, f in chars.items()), key=lambda l: l.freq) def build_tree(letters): """ Run through the list of Letters and build the min heap for the Huffman Tree. """ while len(letters) > 1: left = letters.pop(0) right = letters.pop(0) total_freq = left.freq + right.freq node = TreeNode(total_freq, left, right) letters.append(node) letters.sort(key=lambda l: l.freq) return letters[0] def traverse_tree(root, bitstring): """ Recursively traverse the Huffman Tree to set each Letter's bitstring dictionary, and return the list of Letters """ if type(root) is Letter: root.bitstring[root.letter] = bitstring return [root] letters = [] letters += traverse_tree(root.left, bitstring + "0") letters += traverse_tree(root.right, bitstring + "1") return letters def huffman(file_path): """ Parse the file, build the tree, then run through the file again, using the letters dictionary to find and print out the bitstring for each letter. """ letters_list = parse_file(file_path) root = build_tree(letters_list) letters = { k: v for letter in traverse_tree(root, "") for k, v in letter.bitstring.items() } print(f"Huffman Coding of {file_path}: ") with open(file_path) as f: while True: c = f.read(1) if not c: break print(letters[c], end=" ") print() if __name__ == "__main__": # pass the file path to the huffman function huffman(sys.argv[1])