Validating an IPv4 address

This example will show us how to validate an IP address format, given as an input:

ip_address=input("Enter IP address: ")
#remove any extra characters
ip_address=ip_address.strip()

#initialize a flag to point to true for an ip address
ip_address_flag=True

#validate if there are only 3 dots (.) in ip address
if (not(ip_address.count('.') == 3)):
    ip_address_flag=False
else:
    #Validate if each of the octet is in range 0 - 255
    ip_address=ip_address.split(".")
    for val in ip_address:
        val=int(val)
        if (not(0 <= val <=255)):
            ip_address_flag=False

#based upon the flag value display the relevant message
if (ip_address_flag):
    print ("Given IP is correct")
else:
    print ("Given IP is not correct")

The sample output is as follows:

>>
 Enter IP address: 100.100.100.100
 Given IP is correct
 >>>
 Enter IP address: 2.2.2.258
 Given IP is not correct
 >>>
 Enter IP address: 4.7.2.1.3
 Given IP is not correct
 >>>

As we can see, based upon our validations in the script, the output of our program, returns a validation status of True or False for the IP address that was given as input.

As we move forward, it's important to know that Python, or any programming language, has multiple predefined functions/libraries that can be utilized to perform particular functions. As an example, let's see the earlier example of validating the IPv4 address, using a prebuild library (socket) in Python:

import socket
addr=input("Enter IP address: ")
try:
    socket.inet_aton(addr)
    print ("IP address is valid")
except socket.error:
    print ("IP address is NOT valid")

The sample output is as follows:

>>
 Enter IP address: 100.100.100.100
 IP address is valid
 >>>
 Enter IP address: 2.2.2.258
 IP address is NOT valid
 >>>
 Enter IP address: 4.7.2.1.3
 IP address is NOT valid
 >>>

In the preceding approach, using a prebuilt library helps us to ensure that we do not have to reinvent the wheel (or create our own logic for something that has already been developed by other developers), and also ensures our script remains lean and thin while achieving the same expected results.