Python twos_complement useful functions without ctypes

twos_complement.py

def twos_complement(val, bits):
	"""compute the 2's complement of int value val"""
	if (val & (1 << (bits - 1))) != 0: # if sign bit is set e.g., 8bit: 128-255
		val = val - (1 << bits)        # compute negative value
	return val

def twos_complement_string(val, bits, f):
	if val >= 0:
		return f(twos_complement(val, bits))
	else:
		return f(((abs(val) ^ (2 ** bits - 1)) + 1) & (2 ** bits - 1))