setupcfg

setup.cfg is a configuration file used in Python packaging to configure setuptools and related tools. It uses the INI file format to declare metadata, build options, and tool-specific settings in a declarative style, often allowing projects to avoid embedding configuration in a setup.py script. When present, setup.cfg can be read by setuptools to supply values for the setup() call, either with a minimal setup.py that simply delegates to setuptools, or by some tooling that uses the configuration directly.

The file is organized into sections, each introduced by a header in square brackets. The most common sections are [metadata], which describes the package and its distribution, and [options], which enumerates installation requirements, Python version compatibility, package discovery rules, and packaging options. In [metadata], keys include name, version, description, long_description, url, author, license, classifiers. In [options], keys include packages (often find: to auto-discover packages), install_requires, python_requires, include_package_data, exclude_package_data, and zip_safe. There are also sections such as [options.extras_require] for optional dependencies, and [options.entry_points] for executable scripts and plugins.

setup.cfg is frequently used in conjunction with setup.py, enabling a largely declarative packaging configuration that is easier to read and maintain. With the rise of PEP 517/518 and pyproject.toml, some projects adopt pyproject.toml for build-system requirements, but setup.cfg remains widely supported and common for setuptools-based projects. Limitations include potential incompatibilities with non-Setuptools backends and the need for explicit delegation from setup.py for certain dynamic configurations.