How to create CIDR IP address/Range in IPv4 in python?

Question

How do I convert a IPv4 subnet mask to CIDR range? I have subnet and gateway information available.

Data available:

• Subnet Mask: 255.255.255.0
• Gateway: 192.0.2.250
• Expected CIDR notation: 192.0.2.0/24

I know using ipaddress, CIDR value can be obtained.

from ipaddress import IPv4Network
ip4 = IPv4Network('0/255.255.255.0')
print(ip4.prefixlen)
print(ip4.with_prefixlen)

with results

24
0.0.0.0/24

Answer 1

Pass both your gateway and mask as a tuple to IPv4Network

import ipaddress
gateway = '192.0.2.250'
mask = '255.255.255.0'
network = ipaddress.IPv4Network((gateway, mask), strict=False)
print(network) # 192.0.2.0/24

You must pass strict=False because the network has host bits set