Create and read fixed-point byte representations of numbers in Python

fixed_point.py

import decimal


class FixedPoint(decimal.Decimal):

    def to_fixed_point(self, whole_bits, fraction_bits, signed=False):
        # returns bytes aligned to the last fraction bit
        total = round(self * (1 << fraction_bits))
        num_bytes = (whole_bits + fraction_bits) / 8
        if num_bytes % 1:
            num_bytes = num_bytes + 1
        return total.to_bytes(int(num_bytes), signed=signed, byteorder='big')

    @classmethod
    def from_fixed_point(cls, bytes_, whole_bits, fraction_bits, signed=False):
        value = int.from_bytes(bytes_, byteorder='big', signed=signed)
        if signed and value & sign:
            value = -value
            result = -(value & (sign - 1)) / (1 << fraction_bits)
        else:
            result = value / (1 << fraction_bits)
        return cls.from_float(result)