Python: unsigned 32 bit bitwise arithmetic

Question

Trying to answer to another post whose solution deals with IP addresses and netmasks, I got stuck with plain bitwise arithmetic.

Is there a standard way, in Python, to carry on bitwise AND, OR, XOR, NOT operations assuming that the inputs are "32 bit" (maybe negative) integers or longs, and that the result must be a long in the range [0, 2**32]?

In other words, I need a working Python counterpart to the C bitwise operations between unsigned longs.

EDIT: the specific issue is this:

>>> m = 0xFFFFFF00   # netmask 255.255.255.0 >>> ~m -4294967041L         # wtf?! I want 255 

Answer 1

You can use ctypes and its c_uint32:

>>> import ctypes >>> m = 0xFFFFFF00 >>> ctypes.c_uint32(~m).value 255L 

So what I did here was casting ~m to a C 32-bit unsigned integer and retrieving its value back in Python format.

Answer 2

You can mask everything by 0xFFFFFFFF:

>>> m = 0xFFFFFF00 >>> allf = 0xFFFFFFFF >>> ~m & allf 255L