Python Packaging Guide — A Comprehensive Guide [2026]

Python Packaging Guide A comprehensive reference for packaging, versioning, and publishing Python libraries. 1. pyproject.toml Anatomy pyproject.toml is the single source of truth for modern Python projects (PEP 621). Build System [build-system] requires = ["setuptools> = 68.0 "] build-backend = "setuptools.build_meta" The [build-system] table tells pip and build which backend to use. Alternatives include flit-core , hatchling , and pdm-backend . Project Metadata [project] name = "my-package" # PyPI package name (use hyphens) version = "1.0.0" # Follow semver requires-python = "> = 3.9 " # Minimum Python version dependencies = [ "httpx" ] # Runtime dependencies Key fields: name : Must be unique on PyPI. Use lowercase with hyphens. version : Semantic versioning (MAJOR.MINOR.PATCH). classifiers : Trove classifiers for PyPI search/filtering. optional-dependencies : Groups like [dev] , [docs] . Tool Configuration Tools like ruff, mypy, and pytest read config from [tool.*] tables, keeping e