Convert an IPv4 address in standard (dotted decimal) notation to a decimal number, for educational/entertainment purposes

ipv4.py

#!/usr/bin/env python3
#
# Convert an IPv4 address in standard (dotted decimal) notation to a
# decimal number, for educational/entertainment purposes
# .
#
# E.g.
#
#    vnetman@vnetman-laptop:~/data/bin$ ./ipv4.py 
#    Usage: ./ipv4.py <ipv4 address>
#
#    vnetman@vnetman-laptop:~/data/bin$ ./ipv4.py 8.8.4.4
#    134743044, 0x8080404
#
#    vnetman@vnetman-laptop:~/data/bin$ ping -c 3 134743044
#    PING 134743044 (8.8.4.4) 56(84) bytes of data.
#    64 bytes from 8.8.4.4: icmp_seq=1 ttl=58 time=12.1 ms
#    64 bytes from 8.8.4.4: icmp_seq=2 ttl=58 time=12.0 ms
#    64 bytes from 8.8.4.4: icmp_seq=3 ttl=58 time=12.1 ms
#    
#    --- 134743044 ping statistics ---
#    3 packets transmitted, 3 received, 0% packet loss, time 2002ms
#    rtt min/avg/max/mdev = 12.087/12.132/12.186/0.098 ms
#    vnetman@vnetman-laptop:~/data/bin$ 
#

import sys
import re

if len(sys.argv) != 2:
    print('Usage: {} <ipv4 address>'.format(sys.argv[0]))
    sys.exit(-1)

user_ip = sys.argv[1]

# Parse dotted decimal to individual octets
re_ip_addr = re.compile(r'^(\d{1,3}).(\d{1,3}).(\d{1,3}).(\d{1,3})$')
octets = re_ip_addr.findall(user_ip)
if not octets:
    print('"{}" is not a valid IPv4 address'.format(user_ip))
    sys.exit(-1)

sum = 0
shift = 24
for ostr in octets[0]:
    o = int(ostr)
    if ((o > 255) or (o < 0)):
        print('"{}" is not a valid IPv4 address'.format(user_ip))
        sys.exit(-1)
    sum = sum + (o << shift)
    shift = shift - 8
    
print('{}, {}'.format(str(sum), hex(sum)))