سير العمل البرمجي · التعيين القياسي لشفرات البادئة

def canonical_codes(lengths):
    if type(lengths) is not dict or len(lengths) > 256:
        raise ValueError("codes.input")
    if any(type(s) is not str or not s or type(n) is not int or
           not 1 <= n <= 16 for s,n in lengths.items()):
        raise ValueError("codes.length")
    result, code, previous = {}, 0, 0
    for symbol, length in sorted(lengths.items(), key=lambda p:(p[1],p[0])):
        code <<= length-previous
        if code >= 1 << length:
            raise ValueError("codes.oversubscribed")
        result[symbol] = format(code, f"0{length}b")
        code += 1
        previous = length
    return result