ipaddress.ip_address & properties

Classify an address

Lesson 5 of 20 · 9 min · Module 2: Python’s ipaddress toolkit

You now know how addresses work inside. In real code, Python’s ipaddress module does the careful work for you, for both IPv4 and IPv6.

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By the end, you’ll be able to…

Parse addresses with the ipaddress module
Handle invalid input with try/except
Order checks from most to least specific

The idea

ipaddress.ip_address(text) returns an address object or raises ValueError for invalid text. Objects have properties such as is_loopback (127.0.0.1, ::1) and is_private (10.x, 172.16-31.x, 192.168.x, IPv6 unique local addresses in fc00::/7, and other ranges not routed on the internet).

import ipaddress
address = ipaddress.ip_address("192.168.1.10")
print(address.version, address.is_private)

01One function, two versions

ip_address("::1") returns an IPv6Address and ip_address("10.0.0.1") an IPv4Address. Both have the same properties, so your code works for both.

import ipaddress
print(ipaddress.ip_address("::1").version)

Output

02Invalid input raises ValueError

Instead of returning None, ip_address raises ValueError for text such as "server". Catching it turns a crash into a clear answer.

03Most specific first

127.0.0.1 is both loopback and private. Checking is_loopback first gives the more useful, more specific label.

Your turn

Write classify(text) that returns "invalid" for text that is not an IP address, "loopback" for loopback addresses, "private" for other private addresses, and "public" for everything else. It must work for IPv4 and IPv6.

What the checks look for

Recognises loopback addresses in IPv4 and IPv6
Recognises private addresses
Recognises public addresses
Reports invalid input instead of crashing

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Take this with you

Let the ipaddress module parse and classify; your code decides what the result means.

Go a little further

Add a "link-local" category using is_link_local, for addresses such as 169.254.10.1 and fe80::1.