Month: February 2026

IPs, Python style pt.2

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Hello everyone,

Michael here, and in this post, we’ll continue our exploration of IP addresses using Python’s IP address module!

IP address comparisons

Just as with numbers in Python, you can compare IP address objects in Python too. Here’s how to do it:

import ipaddress
ip1 = ipaddress.ip_address('192.168.1.1')
ip2 = ipaddress.ip_address('192.168.2.1')
ip3 = ipaddress.ip_address('192.168.3.1')
ip4 = ipaddress.ip_address('192.168.1.2')
ip5 = ipaddress.ip_address('192.168.1.3')
print(ip1 < ip2)
print(ip3 > ip2)
print(ip1 < ip4)
print(ip5 > ip4)
True
True
True
True

In this example, we have 5 different IP addresses and ran 4 different comparison operations to see how IP addresses compare to each other. All four of the statements tested returned true, which leads us to conclude:

  • When the first two octets of the IP address stayed the same (192.168), if the third octet of one IP address is greater than another (for instance with ip1 and ip2), then the IP address with the higher third octet (ip2) is “greater than” the IP address with the lower octet (ip1).
  • Similar logic applies to comparing the fourth octet of each IP address. Assuming the first three octets are the same, the fourth octet is then analyzed. In the case of ip5 and ip4, which have the same first three octets, ip5 would be greater than ip4 as the fourth octet of ip5 is “greater than” the fourth octet of ip4.

IP arithmetic

Comparing IP addresses isn’t the only neat thing we can do with the IP address module-in fact, let’s explore another fascinating application of the Python ipaddress module with some IP arithmetic:

print(ipaddress.IPv4Address(u'175.122.13.23') + 18)
print(ipaddress.IPv4Address(u'144.123.100.12') - 15)
print(ipaddress.IPv4Address(u'255.255.255.255') + 1)
print(ipaddress.IPv4Address(u'0.0.0.0') - 1)
175.122.13.41
144.123.99.253
AddressValueError: 4294967296 (>= 2**32) is not permitted as an IPv4 address
AddressValueError: -1 (< 0) is not permitted as an IPv4 address

In this example, we performed basic arithmetic operations on four different IPv4 addresses and while two of them managed to work just fine, the last two operations threw out an AddressValueError exception. Why might that be?

Well, the highest possible IPv4 address is 255.255.255.255. Trying to add even one more bit to this address gave us the AddressValueError exception simply because 255.255.255.255 is the highest possible IPv4 address and thus cannot have anymore bits added to it. Likewise, trying to deduct a bit from 0.0.0.0 also gave us the AddressValueError, as 0.0.0.0 is the lowest possible IPv4 address and trying to deduct a bit isn’t possible.

As for the two successful IPv4 address operations, the first one is quite simple as it simply involves adding 18 bits to the last octet to get 175.122.13.41. The second one on the other hand is a bit more challenging since you can’t have negative bits in an octet (12-15=-3). What would happen then? The previous octet would then be decremented.

Still a little confused? Take the last two octets of the second IP address-100.12-and basically decrement by 15. Decrementing by 12 would give us 100.0 while decrementing by 3 more would give us 99.253 (the first two octets remain unchanged). Since the last octet can’t be less than 0, the “counter” would then go back to 255 for the fourth octet and decrement from there.

Sorting IPs

The last ipaddress module capability I wanted to discuss here is how to sort a list of IPs. Let’s see how we can make that happen:

listOfIPs = ['0.0.0.0', '12.15.33.19', '12.15.34.19', '182.105.99.84', '182.106.100.85', '255.255.255.255']
sorted([ipaddress.ip_address(address) for address in listOfIPs])
[IPv4Address('0.0.0.0'),
 IPv4Address('12.15.33.19'),
 IPv4Address('12.15.34.19'),
 IPv4Address('182.105.99.84'),
 IPv4Address('182.106.100.85'),
 IPv4Address('255.255.255.255')]

It’s quite simple to sort a list of IP addresses. First, let’s assume we have a list of six IPv4 addresses stored as strings in our listOfIPs. How can we sort this list of IPs if all the IPs are stored as strings?

List comprehension to the rescue! By converting each IP-stored-as-a-string to an actual IP address and sorting the list through the sorted() method, you’ll get a nice sorted list of IP addresses?

How does the code know how to perfectly sort these IP addresses? When it comes to sorting IP addresses, 0.0.0.0 and 255.255.255.255 are the lowest and highest possible IPv4 addresses, respectively. The other four IP addresses in between are sorted by the value of their octets in either right-to-left or left-to-right order, depending on the values of each IP address’s octets. In other words, 12.15.34.19 is greater than 12.15.33.19 because even though both IP addresses share the same fourth octet, the third octet of 12.15.34.19 (34) is greater than the third octet of 12.15.33.19 (33).

Similar logic applies to the IP addresses 182.105.99.84 and 182.106.100.85 because even though the first octet of both IP addresses is the same, the other three octets of 182.106.100.85 are still greater than the other three octets of 182.105.99.84.

Here’s the link to today’s code in GitHub-https://github.com/mfletcher2021/blogcode/blob/main/IP_addresses_pt_2.ipynb

Thanks for reading,

Michael