Regexp to check if an IP is valid

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I'm wondering if it's possible to compare values in regexps with the regexp system in Python. Matching the pattern of an IP is easy, but each 1-3 digits cannot be above 255 and that's where I'm a bit stumped.


You need to check the allowed numbers in each position. For the first optional digit, acceptable values are 0-2. For the second, 0-5 (if the first digit for that part is present, otherwise 0-9), and 0-9 for the third.

I found this annotated example at http://www.regular-expressions.info/regexbuddy/ipaccurate.html :

\b(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\b

Validating IPv4 addresses with regexp, Here I have taken the value of ip and I am trying to match it with regex. Above condition checks if the value exceeds 255 for all the 4 octets then it is not a valid. Matching an IP address is another good example of a trade-off between regex complexity and exactness. \b \d {1,3} \. \d {1,3} \. \d {1,3} \. \d {1,3} \b will match any IP address just fine. But will also match 999.999.999.999 as if it were a valid IP address. If your regex flavor supports Unicode, it may even match ١٢٣.१२३.೧೨೩.๑๒๓. Whether this is a problem depends on the files or data you intend to apply the regex to.


No need for regular expressions here. Some background:

>>> import socket
>>> socket.inet_aton('255.255.255.255')
'\xff\xff\xff\xff'
>>> socket.inet_aton('255.255.255.256')
Traceback (most recent call last):
  File "<input>", line 1, in <module>
error: illegal IP address string passed to inet_aton
>>> socket.inet_aton('my name is nobody')
Traceback (most recent call last):
  File "<input>", line 1, in <module>
error: illegal IP address string passed to inet_aton

So:

import socket

def ip_address_is_valid(address):
    try: socket.inet_aton(address)
    except socket.error: return False
    else: return True

Note that addresses like '127.1' could be acceptable on your machine (there are systems, including MS Windows and Linux, where missing octets are interpreted as zero, so '127.1' is equivalent to '127.0.0.1', and '10.1.4' is equivalent to '10.1.0.4'). Should you require that there are always 4 octets, change the last line from:

else: return True

into:

else: return address.count('.') == 3

Validate an ip address, RegEx for Check whether a string is a valid ip address. . # repeat with 3 times (3x) $ #end of the line Whole combination means, digit from 0 to 255 and follow by a dot “.”, repeat 4 time and ending with no dot “.” Valid IP address format is “0-255.0-255.0-255.0-255”. 1.


You can check a 4-octet IP address easily without regexes at all. Here's a tested working method:

>>> def valid_ip(ip):
...    parts = ip.split('.')
...    return (
...        len(parts) == 4
...        and all(part.isdigit() for part in parts)
...        and all(0 <= int(part) <= 255 for part in parts)
...        )
...
>>> valid_ip('1.2.3.4')
True
>>> valid_ip('1.2.3.4.5')
False
>>> valid_ip('1.2.   3   .4.5')
False
>>> valid_ip('1.256.3.4.5')
False
>>> valid_ip('1.B.3.4')
False
>>>

Validate an ip address, Regular Expression to Check whether a string is a valid ip address. Prerequisite: Python Regex. Given an IP address as input, write a Python program to check whether the given IP Address is Valid or not. What is an IP (Internet Protocol) Address ? Every computer connected to the Internet is identified by a unique four-part string, known as its Internet Protocol (IP) address.


Regex is for pattern matching, but to check for a valid IP, you need to check for the range (i.e. 0 <= n <= 255).

You may use regex to check for range, but that'll be a bit overkill. I think you're better off checking for basic patter and then check for the range for each number.

For example, use the following pattern to match an IP:

([0-9]{1,3})\.([0-9]{1,3})\.([0-9]{1,3})\.([0-9]{1,3})

Then check whether each number is within range.

7.16. Matching IPv4 Addresses, Problem. You want to check whether a certain string represents a valid IPv4 address in 255.255.255.255 notation. Simple regex to check for an IP address: ^(? This regular expression is too simple - if you want to it to be accurate, you need to check that the numbers are between 0 and 255, with the regex above accepting 444 in any position. You want to check for 250-255 with 25 [0-5], or any other 200 value 2 [0-4] [0-9], or any 100 value or less with ? [0-9] [0-9].


The following supports IPv4, IPv6 as well as Python 2.7 & 3.3

import socket


def is_valid_ipv4(ip_str):
    """
    Check the validity of an IPv4 address
    """
    try:
        socket.inet_pton(socket.AF_INET, ip_str)
    except AttributeError:
        try:
            socket.inet_aton(ip_str)
        except socket.error:
            return False
        return ip_str.count('.') == 3
    except socket.error:
        return False
    return True


def is_valid_ipv6(ip_str):
    """
    Check the validity of an IPv6 address
    """
    try:
        socket.inet_pton(socket.AF_INET6, ip_str)
    except socket.error:
        return False
    return True


def is_valid_ip(ip_str):
    """
    Check the validity of an IP address
    """
    return is_valid_ipv4(ip_str) or is_valid_ipv6(ip_str)

How to validate an IP address using Regular Expressions in Java , Return true if the string matches with the given regex, else return false. Below is the implementation of the above approach:. Unix & Linux Stack Exchange is a question and answer site for users of Linux, FreeBSD and other Un*x-like operating systems. Your regex cannot match the valid IP


Python program to validate an IP Address, Prerequisite: Python Regex. Given an IP address as input, write a Python program to check whether the given IP Address is Valid or not. What is an IP (​Internet  7.16. Matching IPv4 Addresses Problem You want to check whether a certain string represents a valid IPv4 address in 255.255.255.255 notation. Optionally, you want to convert this address into a … - Selection from Regular Expressions Cookbook [Book]


How to validate IP address with regular expression, Validate ip address with regular expression * @param ip ip address for validation * @return true valid ip address, false invalid ip address  An example of a valid IP is: 192.168.4.1 To validate the IP address we should follow these steps Tokenize the string (IP address) using the dot “.” delimiter If the sub strings are containing any non-numeric character, then return false


JavaScript : IP address validation, Example of valid IP address. 115.42.150.37; 192.168. Explanation of the said Regular expression (IP address). Regular Expression Previous: JavaScript : HTML Form validation - checking for password. Next: JavaScript  IP address validation. Every computer connected to the Internet is identified by a unique four-part string, known as its Internet Protocol (IP) address. An IP address consists of four numbers (each between 0 and 255) separated by periods.