best_fit_ip_mask.py

from ipaddress import ip_address

def main():
	print(get_mask_length('192.168.5.65', '192.168.5.111'))
	print(get_mask_length('2001:dead::', '2001:dead:beef::'))
	
def get_mask_length(ip1, ip2):
	ip1_int = int(ip_address(ip1))
	ip2_int = int(ip_address(ip2))
	unique_bits_int = abs(ip1_int - ip2_int)  + 1 #add 1 to be inclusive of both addresses
	
	return ip_address(ip1).max_prefixlen - len('{:b}'.format(unique_bits_int))

if __name__ == '__main__':
	main()