Get IP Mask from IP Address and Mask Length in Python

Question

Given an IP Address in dotted quad notation, for example:
192.192.45.1
And a mask length for example 8, 16, 24 typically, but could be anything i.e. 17.

Ca

Answer 1

You can calcuate the 32 bit value of the mask like this

(1<<32) - (1<<32>>mask_length)

eg.

>>> import socket, struct
>>> mask_length = 24
>>> mask = (1<<32) - (1<<32>>mask_length)
>>> socket.inet_ntoa(struct.pack(">L", mask))
'255.255.255.0'