Regular expression that matches valid IPv6 addresses

Answer 1

It sounds like you may be using Python. If so, you can use something like this:

import socket

def check_ipv6(n):
    try:
        socket.inet_pton(socket.AF_INET6, n)
        return True
    except socket.error:
        return False

print check_ipv6('::1') # True
print check_ipv6('foo') # False
print check_ipv6(5)     # TypeError exception
print check_ipv6(None)  # TypeError exception

I don't think you have to have IPv6 compiled in to Python to get inet_pton, which can also parse IPv4 addresses if you pass in socket.AF_INET as the first parameter. Note: this may not work on non-Unix systems.