Validate IP Address using RegEx in Python

Aniruddha Chaudhari/9834/9
CodePython

Problem Statement: Write a Python program to validate if the given string is a valid IP address or not.

This is one of the questions asked in the Juniper coding interview.

In Computer Network, the IP address uniquely defines each host or node in the network. You can read mode about IP address in Computer Networking.

Basically, this is a pattern matching problem where we can use a regular expression (RegEx).

IP Address Validation using Python RegEx

Here we are using the search method from the re module. You can find more detail in the Python RegEx tutorial.

Method 1: Using RegEx

Code

import re 
  
regexIP = '''^(25[0-5]|2[0-4][0-9]|[0-1]?[0-9][0-9]?)\.( 
    25[0-5]|2[0-4][0-9]|[0-1]?[0-9][0-9]?)\.( 
    25[0-5]|2[0-4][0-9]|[0-1]?[0-9][0-9]?)\.( 
    25[0-5]|2[0-4][0-9]|[0-1]?[0-9][0-9]?)'''
  
def validateIP(strIP): 
  
    if(re.search(regexIP, strIP)):
        print(f"{strIP} is a valid IP address.") 
      
    else: 
        print(f"{strIP} is an invalid IP address.") 
  
  
if __name__ == '__main__' : 
      
    strIP = "122.134.3.123"
    validateIP(strIP) 
  
    strIP = "44.235.34.1"
    validateIP(strIP) 
  
    strIP = "277.13.23.17"
    validateIP(strIP)

Output

122.134.3.123 is a valid IP address. 
44.235.34.1 is a valid IP address.
277.13.23.17 is an invalid IP address.

Note: When we say IP address, by default it’s IPv4 address which is different from IPv6 address.

Method 2: Without RegEx

Python Code:

(This solution is shared by Mallikarjuna.)

def validate_ip(ip):
    part = ip.split(".")
    if not (len(part) == 4):
        return False
    for i in part:
        if int(i) > 255:
            return False
        if not isinstance(int(i),int):
            return False
    return True
    
if __name__ == "__main__":
    ip = "10.10.10.40"
    out = validate_ip(ip)
    if out:
        print(f"{ip} is valid IP.")
    else:
        print(f"{ip} is invalid IP.")

This is a simple program to validate IP address using regex in Python. Do you have any other solutions? Let me know in the comment. Thanks!

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Aniruddha Chaudhari
I am complete Python Nut, love Linux and vim as an editor. I hold a Master of Computer Science from NIT Trichy. I dabble in C/C++, Java too. I keep sharing my coding knowledge and my own experience on CSEstack.org portal.
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Comments

  • Reply
    Rajat
    April 11, 2021 at 11:33 pm

    It says it’s valid – 122.134.3.0991 is a valid IP address.

    Can you test with this string – strIP = “122.134.3.0991”?

    • Reply
      Aniruddha Chaudhari
      April 17, 2021 at 10:38 am

      Thanks for identifying it. Looks like we also have to check the length of each octave.

  • Reply
    Malan
    May 31, 2021 at 10:37 pm

    Just add $ in the end.

    • Reply
      Aniruddha Chaudhari
      June 1, 2021 at 12:49 pm

      Not sure where do you want to add $. The code is working. You can try executing code on our online CSEstack IDE.

  • Reply
    Mallikarjuna
    August 7, 2021 at 2:23 pm 
    out = "10.10.10.40"
part = out.split(".")
if len(part) > 4:
    print("invalid")
for i in part:
    if int(i)  255:
        print("invalid")
    if not isinstance(int(i),int):
        print("invalid")
print("valid")
    • Reply
      Aniruddha Chaudhari
      August 9, 2021 at 8:57 am

      This is a truly simple and easy solution. Thanks for sharing. Here problem statement is to write the regex expression to check the valid IP address.

      • Reply
        Raamesh
        July 30, 2022 at 12:55 am 
        #ip = "122.134.3.0991"
ip ="10.49.121.22"
part = ip.split(".")
if len(part) == 4:
    print('''It's a Valid IPv4 format''')
    c=0
    for i in part:
        if int(i) < 255:
            c = c+1
    if c == 4:
       print("A valid IP Address")
    else:
       print("Invalid IP Address&quot")    
        
else:
    print("""It's completely an Invalid IPv4 format""")
        • Reply
          Aniruddha Chaudhari
          July 30, 2022 at 12:02 pm

          This solution looks very good without regex expression.

  • Reply
    Raamesh
    August 1, 2022 at 2:46 am 
    import re
c=0
ipadd="10.049.204.1"
ip=ipadd.split('.')
exp ='(2[0-5][0-4]|[01](\d?){2}|(\d?){2})'
for i in ip:
    print(i)
    if(re.fullmatch(exp,i)):
        c=c+1
if c==4:
    print("It is a valid IP")
else:
    print("An invalid IP")

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