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PKG009-classifiers-missing — Missing PyPI Classifiers

Dimension: Packaging Default severity: Low Languages: All (project-level) Last reviewed: 2026-05-08

What it detects​

Emits when [project] in pyproject.toml has no classifiers field or has a classifiers array that does not contain at least one Programming Language :: Python :: 3 (or 3.x) classifier.

Why it matters​

PyPI classifiers are metadata tags that:

  • Allow users to filter packages by Python version, OS, topic, and development status on the PyPI search interface.
  • Signal to pip (and other resolvers) which Python versions and implementations are supported.
  • Enable automated tooling (bandersnatch, devpi, pip's --python-requires filtering) to correctly handle compatibility.

A package without a Python version classifier will not appear in version- filtered searches and cannot benefit from pip's interpreter-compatibility checks.

Configuration​

No configuration knobs in v1.

Example — flagged​

[project]
name = "my-package"
version = "1.0.0"
# No classifiers at all — flagged
[project]
name = "my-package"
version = "1.0.0"
classifiers = [
    "License :: OSI Approved :: MIT License",
    # No Python version classifier — flagged
]

Example — not flagged​

[project]
name = "my-package"
version = "1.0.0"
classifiers = [
    "Programming Language :: Python :: 3",
    "Programming Language :: Python :: 3.11",
    "License :: OSI Approved :: MIT License",
]

Fix guidance​

Add a classifiers array to [project] with at minimum a Python version classifier and a development status classifier:

[project]
classifiers = [
    "Development Status :: 4 - Beta",
    "Intended Audience :: Developers",
    "License :: OSI Approved :: MIT License",
    "Programming Language :: Python :: 3",
    "Programming Language :: Python :: 3.9",
    "Programming Language :: Python :: 3.10",
    "Programming Language :: Python :: 3.11",
    "Programming Language :: Python :: 3.12",
]

The full list of valid classifiers is available at pypi.org/classifiers/.

Implementation​

Source: crates/zuit-lang-python/src/analyzers/pkg/pkg009_classifiers_missing.rs

References​