pyprojecttoml

pyproject.toml is a configuration file at the root of Python projects used to declare build system requirements and project metadata in the TOML format. Introduced by PEP 518 to standardize how builds are described and performed, it serves as a central place that packaging tools can read without executing setup.py. Its use was extended by PEP 621, which defines a standard project metadata table, and by other PEPs to improve interoperability among tools.

The file is organized into TOML tables. The essential table is [build-system], which lists build-backend and requires, the latter being a list of packages needed to build the project. The build-backend specifies the import path of the build backend, such as setuptools.build_meta, or a tool-specific backend used by Poetry, Flit, or others.

Another important table is [project] (per PEP 621), which can contain standard metadata fields such as name, version, description, readme, license, authors, and classifiers. Not all toolchains require this section, and some projects may populate metadata in tool-specific sections like [tool.poetry], depending on the tooling in use.

In practice, pyproject.toml enables build isolation and simplifies packaging workflows. It allows tools to declare their own configuration under [tool.*] sections, for example [tool.poetry] for Poetry-managed projects or [tool.flit] for Flit. This TOML file is typically committed to version control and shared across environments, ensuring consistent builds across platforms.

Overall, pyproject.toml has become a cornerstone of modern Python packaging by consolidating build configuration and, where supported, project metadata in a single, machine-readable file.