Implementation:Scikit learn Scikit learn PackagingVersion

Knowledge Sources	Scikit_learn Scikit-learn Docs
Domains	Utilities, Packaging
Last Updated	2026-02-08 15:00 GMT

Overview

Concrete tool for parsing and comparing PEP 440 version strings provided by scikit-learn (vendored from the packaging library).

Description

This module is a vendored copy of the packaging library's version module. It provides the Version class for parsing PEP 440-compliant version strings and comparing them. It also includes the LegacyVersion class for handling non-PEP 440 version strings. The module defines a parse() function that returns the appropriate version object and supports all PEP 440 version specifiers including pre-releases, post-releases, dev releases, and local versions.

Usage

Use this module to parse, compare, and validate Python package version strings within scikit-learn's codebase without requiring the external packaging library as a runtime dependency.

Code Reference

Source Location

• Repository: scikit-learn
• File: sklearn/externals/_packaging/version.py

Signature

def parse(version: str) -> Union["LegacyVersion", "Version"]:
    ...

class Version(_BaseVersion):
    _regex = re.compile(r"^\s*" + VERSION_PATTERN + r"\s*$", re.VERBOSE | re.IGNORECASE)

    def __init__(self, version: str) -> None:
        ...

class LegacyVersion(_BaseVersion):
    def __init__(self, version: str) -> None:
        ...

Import

from sklearn.externals._packaging.version import parse, Version

I/O Contract

Inputs

Name	Type	Required	Description
version	str	Yes	Version string to parse (e.g., '1.2.3', '2.0.0rc1')

Outputs

Name	Type	Description
Version	Version or LegacyVersion	Parsed version object supporting comparison operators
major	int	Major version number
minor	int	Minor version number
micro	int	Micro (patch) version number
is_prerelease	bool	Whether this is a pre-release version

Usage Examples

Basic Usage

from sklearn.externals._packaging.version import parse, Version

v1 = parse("1.2.3")
v2 = parse("1.3.0")
print(v1 < v2)   # True
print(v1.major)   # 1
print(v1.minor)   # 2

# Direct Version class usage
v = Version("2.0.0rc1")
print(v.is_prerelease)  # True

Related Pages

• Principle:Scikit_learn_Scikit_learn_Dataset_Loading