PyPA Specifications

Page Status:Complete
Last Reviewed:2017-02-06

This is a list of currently active interoperability specifications maintained by the Python Packaging Authority.

Package distribution metadata

Core metadata

The current core metadata file format, version 1.2, is specified in PEP 345.

However, the version specifiers and environment markers sections of that PEP have been superceded as described below. In addition, metadata files are permitted to contain the following additional field:

Provides-Extra (multiple use)

A string containing the name of an optional feature. Must be a valid Python identifier. May be used to make a dependency conditional on whether the optional feature has been requested.


Provides-Extra: pdf
Requires-Dist: reportlab; extra == 'pdf'

A second distribution requires an optional dependency by placing it inside square brackets, and can request multiple features by separating them with a comma (,). The requirements are evaluated for each requested feature and added to the set of requirements for the distribution.


Requires-Dist: beaglevote[pdf]
Requires-Dist: libexample[test, doc]

Two feature names test and doc are reserved to mark dependencies that are needed for running automated tests and generating documentation, respectively.

It is legal to specify Provides-Extra: without referencing it in any Requires-Dist:.

Version Specifiers

Version numbering requirements and the semantics for specifying comparisons between versions are defined in PEP 440.

The version specifiers section in this PEP supersedes the version specifiers section in PEP 345.

Dependency Specifiers

The dependency specifier format used to declare a dependency on another component is defined in PEP 508.

The environment markers section in this PEP supersedes the environment markers section in PEP 345.

Declaring Build System Dependencies

pyproject.toml is a build system independent file format defined in PEP 518 that projects may provide in order to declare any Python level dependencies that must be installed in order to run the project’s build system successfully.

Source Distribution Format

The source distribution format (sdist) is not currently formally defined. Instead, its format is implicitly defined by the behaviour of the standard library’s distutils module when executing the sdist command.

Binary Distribution Format

The binary distribution format (wheel) is defined in PEP 427.

Platform Compatibility Tags

The platform compatibility tagging model used for wheel distribution is defined in PEP 425.

The scheme defined in that PEP is insufficient for public distribution of Linux wheel files (and *nix wheel files in general), so PEP 513 was created to define the manylinux1 tag.

Recording Installed Distributions

The format used to record installed packages and their contents is defined in PEP 376.

Note that only the dist-info directory and the RECORD file format from that PEP are currently implemented in the default packaging toolchain.

Package index interfaces

Simple repository API

The current interface for querying available package versions and retrieving packages from an index server is defined in PEP 503.