How to Accurately Compare Version Numbers in Python?

Comparing Version Numbers in Python

In Python, it's often necessary to compare versions, especially when working with package management or tracking software dependencies. However, directly comparing string versions can lead to incorrect results due to lexicographic ordering.

Using packaging.version.Version

The recommended solution is to use the packaging.version.Version class from the packaging library. This class provides support for PEP 440 style ordering, ensuring that versions are properly compared according to the rules defined by the Python Packaging Authority.

import packaging.version as version

version("2.3.1") < version("10.1.2")
# True

version("1.3.a4") < version("10.1.2")
# True

Alternatives

Prior to the availability of packaging, the distutils.version module was used for version comparison. However, it has been deprecated and conforms to the now superseded PEP 386. It's recommended to avoid using this module and rely on packaging.version.Version instead.

Deprecated DISTutils.version Module

from distutils.version import LooseVersion, StrictVersion

LooseVersion("2.3.1") < LooseVersion("10.1.2")
# True

StrictVersion("2.3.1") < StrictVersion("10.1.2")
# True

StrictVersion("1.3.a4")
# ValueError: invalid version number '1.3.a4'

Note that StrictVersion does not support PEP 440 versions, considering them as "not strict."

Conclusion

When comparing version numbers in Python, prefer the packaging.version.Version class for accurate and reliable results. It follows the latest PEP 440 specifications and ensures consistent version ordering. Avoid using the deprecated distutils.version module, which may produce incorrect comparisons.

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