Subnet merge show right subnets which are not in left subnets

subnet_merge.py

import sys
from netaddr import IPNetwork
from pprint import pprint
 
# right must be in left
def main(left_side, right_side):
 
    with open(right_side, "r") as f:
        raw_right = f.readlines()
 
    with open(left_side, "r") as f:
        raw_left = f.readlines()
 
    right = []
    left = []
    not_found = []
 
    # clean lines
    for line in raw_right:
        right.append(line.strip())
 
    for line in raw_left:
        left.append(line.strip())
 
    try:
        for r in right:
            FOUND = False
            for l in left:
                if IPNetwork(r) in IPNetwork(l):
                    FOUND = True
                    print(f"Found {r} in {l}")
 
            if FOUND is False:
                not_found.append(r)
 
    except Exception as e:
        print(e)
 
    pprint(not_found)
 
 
if __name__ == "__main__":
    main(sys.argv[1], sys.argv[2])