How to validate IP address in Python

[bkunjitam]

Hi,

My programme has a text box where in user enters the ip address. I need to validate the IP (like no space allowed in the entry, the numerals should not exceed 255, not more than 3 dots allowed overall, no consecutive dots allowed etc.,.). How do i go about the same? Is there any built in function for the same?

thanks,
Badri

[bvdet]

Hi,

My programme has a text box where in user enters the ip address. I need to validate the IP (like no space allowed in the entry, the numerals should not exceed 255, not more than 3 dots allowed overall, no consecutive dots allowed etc.,.). How do i go about the same? Is there any built in function for the same?

thanks,
Badri

Badri,

This may cover most of of your requirements:

ip_str = "23.34.45.45"
 
def ipFormatChk(ip_str):
    if len(ip_str.split()) == 1:
        ipList = ip_str.split('.')
        if len(ipList) == 4:
            for i, item in enumerate(ipList):
                try:
                    ipList[i] = int(item)
                except:
                    return False
                if not isinstance(ipList[i], int):
                    return False
            if max(ipList) < 256:
                return True
            else:
                return False
        else:
            return False
    else:
        return False
 
print ipFormatChk(ip_str)
True

[bartonc]

Nice coding, BV!

Badri,

This may cover most of of your requirements:

ip_str = "23.34.45.45"
 
def ipFormatChk(ip_str):
    if len(ip_str.split()) == 1:
        ipList = ip_str.split('.')
        if len(ipList) == 4:
            for i, item in enumerate(ipList):
                try:
                    ipList[i] = int(item)
                except:
                    return False
                if not isinstance(ipList[i], int):
                    return False
            if max(ipList) < 256:
                return True
            else:
                return False
        else:
            return False
    else:
        return False
 
print ipFormatChk(ip_str)
True

[MDunderdale]

You can also use regular expressions like this

import re
ip_str = "23.34.45.45"
 
def ipFormatChk(ip_str):
   pattern = r"\b(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\b"
   if re.match(pattern, ip_str):
      return True
   else:
      return False
print ipFormatChk(ip_str)
 

[bvdet]

You can also use regular expressions like this

import re
ip_str = "23.34.45.45"
 
def ipFormatChk(ip_str):
   pattern = r"\b(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\b"
   if re.match(pattern, ip_str):
      return True
   else:
      return False
print ipFormatChk(ip_str)
 

Regular expressions are ideal for this application. This code executes much faster than the other. The drawback is readability. An alternative is to set the VERBOSE flag and add comments:

pattern = re.compile(r"""
   \b                                           # matches the beginning of the string
   (25[0-5]|                                    # matches the integer range 250-255 OR
   2[0-4][0-9]|                                 # matches the integer range 200-249 OR
   [01]?[0-9][0-9]?)                            # matches any other combination of 1-3 digits below 200
   \.                                           # matches '.'
   (25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)       # repeat
   \.                                           # matches '.'
   (25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)       # repeat
   \.                                           # matches '.'
   (25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)       # repeat
   \b                                           # matches the end of the string
   """, re.VERBOSE)

It executes slower, but I guess you can't have everything! Thanks for posting Mike.

[bartonc]

Regular expressions are ideal for this application. This code executes much faster than the other. The drawback is readability. An alternative is to set the VERBOSE flag and add comments:

pattern = re.compile(r"""
   \b                                           # matches the beginning of the string
   (25[0-5]|                                    # matches the integer range 250-255 OR
   2[0-4][0-9]|                                 # matches the integer range 200-249 OR
   [01]?[0-9][0-9]?)                            # matches any other combination of 1-3 digits below 200
   \.                                           # matches '.'
   (25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)       # repeat
   \.                                           # matches '.'
   (25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)       # repeat
   \.                                           # matches '.'
   (25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)       # repeat
   \b                                           # matches the end of the string
   """, re.VERBOSE)

It executes slower, but I guess you can't have everything! Thanks for posting Mike.

I like you style, BV.