Find netrange from two IP addresses

get_netrange.py

import ipaddress

def ip_in_network(startIp, endIp):
    mask = 32
    startIp = ipaddress.ip_address(startIp)
    endIp = ipaddress.ip_address(endIp)
    netrange = ipaddress.ip_network(str(startIp)+'/'+str(mask), strict=False)
    while ((endIp in netrange) == False):
        mask -= 1
        netrange = ipaddress.ip_network(str(startIp)+'/'+str(mask), strict=False)
    return netrange

Couple notes, it's generally considered more idiomatic to use string formatting rather than concatenation. This is usually easier to read and you don't need to explicitly convert to str. (It's also more efficient due to how strings are implemented.)

So str(startIp)+'/'+str(mask) could be written as '{}/{}'.format(startIp, mask).

Also, instead of while ((endIp in netrange) == False) you can write while endIp not in netrange.

Another option would be to write it as a for loop. I prefer this because it's shorter and reduces duplicate code, but it's really personally preference.

import ipaddress

def ip_in_network(startIp, endIp):
    startIp = ipaddress.ip_address(startIp)
    endIp = ipaddress.ip_address(endIp)
    for mask in range(32, -1, -1):
        netrange = ipaddress.ip_network('{}/{}'.format(startIp, mask), strict=False)
        if endIp in netrange:
            return netrange

(The range statement creates a list going from 32 to 0.)