What's the best way to validate that an IP entered by the user is valid? It comes in as a string.
It looks like you are trying to validate IP addresses. A regular expression is probably not the best tool for this.
from IPy import IP IP('127.0.0.1')
If the IP address is invalid it will throw an exception.
Or you could use
import socket try: socket.inet_aton(addr) # legal except socket.error: # Not legal
If you really want to only match IPv4 with 4 decimal parts then you can split on dot and test that each part is an integer between 0 and 255.
def validate_ip(s): a = s.split('.') if len(a) != 4: return False for x in a: if not x.isdigit(): return False i = int(x) if i < 0 or i > 255: return False return True
Note that your regular expression doesn't do this extra check. It would accept
999.999.999.999 as a valid address.
If you use Python3, you can use
ipaddress module http://docs.python.org/py3k/library/ipaddress.html. Example:
>>> import ipaddress >>> ipv6 = "2001:0db8:0a0b:12f0:0000:0000:0000:0001" >>> ipv4 = "192.168.2.10" >>> ipv4invalid = "2184.108.40.206" >>> str = "Tay Tay" >>> ipaddress.ip_address(ipv6) IPv6Address('2001:db8:a0b:12f0::1') >>> ipaddress.ip_address(ipv4) IPv4Address('192.168.2.10') >>> ipaddress.ip_address(ipv4invalid) Traceback (most recent call last): File "<console>", line 1, in <module> File "/usr/lib/python3.4/ipaddress.py", line 54, in ip_address address) ValueError: '2220.127.116.11' does not appear to be an IPv4 or IPv6 address >>> ipaddress.ip_address(str) Traceback (most recent call last): File "<console>", line 1, in <module> File "/usr/lib/python3.4/ipaddress.py", line 54, in ip_address address) ValueError: 'Tay Tay' does not appear to be an IPv4 or IPv6 address