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copied!<pre><code>def is_valid_ip(ip): """Validates IP addresses. """ return is_valid_ipv4(ip) or is_valid_ipv6(ip) </code></pre> <p>IPv4:</p> <pre><code>def is_valid_ipv4(ip): """Validates IPv4 addresses. """ pattern = re.compile(r""" ^ (?: # Dotted variants: (?: # Decimal 1-255 (no leading 0's) [3-9]\d?|2(?:5[0-5]|[0-4]?\d)?|1\d{0,2} | 0x0*[0-9a-f]{1,2} # Hexadecimal 0x0 - 0xFF (possible leading 0's) | 0+[1-3]?[0-7]{0,2} # Octal 0 - 0377 (possible leading 0's) ) (?: # Repeat 0-3 times, separated by a dot \. (?: [3-9]\d?|2(?:5[0-5]|[0-4]?\d)?|1\d{0,2} | 0x0*[0-9a-f]{1,2} | 0+[1-3]?[0-7]{0,2} ) ){0,3} | 0x0*[0-9a-f]{1,8} # Hexadecimal notation, 0x0 - 0xffffffff | 0+[0-3]?[0-7]{0,10} # Octal notation, 0 - 037777777777 | # Decimal notation, 1-4294967295: 429496729[0-5]|42949672[0-8]\d|4294967[01]\d\d|429496[0-6]\d{3}| 42949[0-5]\d{4}|4294[0-8]\d{5}|429[0-3]\d{6}|42[0-8]\d{7}| 4[01]\d{8}|[1-3]\d{0,9}|[4-9]\d{0,8} ) $ """, re.VERBOSE | re.IGNORECASE) return pattern.match(ip) is not None </code></pre> <p>IPv6:</p> <pre><code>def is_valid_ipv6(ip): """Validates IPv6 addresses. """ pattern = re.compile(r""" ^ \s* # Leading whitespace (?!.*::.*::) # Only a single whildcard allowed (?:(?!:)|:(?=:)) # Colon iff it would be part of a wildcard (?: # Repeat 6 times: [0-9a-f]{0,4} # A group of at most four hexadecimal digits (?:(?<=::)|(?<!::):) # Colon unless preceeded by wildcard ){6} # (?: # Either [0-9a-f]{0,4} # Another group (?:(?<=::)|(?<!::):) # Colon unless preceeded by wildcard [0-9a-f]{0,4} # Last group (?: (?<=::) # Colon iff preceeded by exacly one colon | (?<!:) # | (?<=:) (?<!::) : # ) # OR | # A v4 address with NO leading zeros (?:25[0-4]|2[0-4]\d|1\d\d|[1-9]?\d) (?: \. (?:25[0-4]|2[0-4]\d|1\d\d|[1-9]?\d) ){3} ) \s* # Trailing whitespace $ """, re.VERBOSE | re.IGNORECASE | re.DOTALL) return pattern.match(ip) is not None </code></pre> <p>The IPv6 version uses "<code>(?:(?<=::)|(?<!::):)</code>", which could be replaced with "<code>(?(?<!::):)</code>" on regex engines that support conditionals with look-arounds. (i.e. PCRE, .NET)</p> <p><strong>Edit:</strong></p> <ul> <li>Dropped the native variant.</li> <li>Expanded the regex to comply with the RFC.</li> <li>Added another regex for IPv6 addresses.</li> </ul> <p><strong>Edit2:</strong></p> <p>I found some links discussing how to parse IPv6 addresses with regex:</p> <ul> <li><a href="http://forums.dartware.com/viewtopic.php?t=452" rel="noreferrer">A Regular Expression for IPv6 Addresses</a> - InterMapper Forums</li> <li><a href="http://www.vankouteren.eu/blog/2009/05/working-ipv6-regular-expression/" rel="noreferrer">Working IPv6 regular expression</a> - Patrick’s playground blog</li> <li><a href="http://download.dartware.com/thirdparty/test-ipv6-regex.pl" rel="noreferrer">test-ipv6-regex.pl</a> - Perl script with tons of test-cases. It seems my regex fails on a few of those tests.</li> </ul> <p><strong>Edit3:</strong></p> <p>Finally managed to write a pattern that passes all tests, and that I am also happy with.</p>

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