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Python Enhancement Proposals

PEP 314 – Metadata for Python Software Packages 1.1

A.M. Kuchling, Richard Jones
Distutils-SIG list
Standards Track

Table of Contents


This PEP describes a mechanism for adding metadata to Python packages. It includes specifics of the field names, and their semantics and usage.

This document specifies version 1.1 of the metadata format. Version 1.0 is specified in PEP 241.

Including Metadata in Packages

The Distutils sdist command will extract the metadata fields from the arguments and write them to a file in the generated zipfile or tarball. This file will be named PKG-INFO and will be placed in the top directory of the source distribution (where the README, INSTALL, and other files usually go).

Developers may not provide their own PKG-INFO file. The sdist command will, if it detects an existing PKG-INFO file, terminate with an appropriate error message. This should prevent confusion caused by the PKG-INFO and files being out of sync.

The PKG-INFO file format is a single set of RFC 822 headers parseable by the module. The field names listed in the following section are used as the header names.


This section specifies the names and semantics of each of the supported metadata fields.

Fields marked with “(Multiple use)” may be specified multiple times in a single PKG-INFO file. Other fields may only occur once in a PKG-INFO file. Fields marked with “(optional)” are not required to appear in a valid PKG-INFO file; all other fields must be present.


Version of the file format; currently “1.0” and “1.1” are the only legal values here.


Metadata-Version: 1.1


The name of the package.


Name: BeagleVote


A string containing the package’s version number. This field should be parseable by one of the Version classes (StrictVersion or LooseVersion) in the distutils.version module.


Version: 1.0a2

Platform (multiple use)

A comma-separated list of platform specifications, summarizing the operating systems supported by the package which are not listed in the “Operating System” Trove classifiers. See “Classifier” below.


Platform: ObscureUnix, RareDOS

Supported-Platform (multiple use)

Binary distributions containing a PKG-INFO file will use the Supported-Platform field in their metadata to specify the OS and CPU for which the binary package was compiled. The semantics of the Supported-Platform field are not specified in this PEP.


Supported-Platform: RedHat 7.2
Supported-Platform: i386-win32-2791


A one-line summary of what the package does.


Summary: A module for collecting votes from beagles.

Description (optional)

A longer description of the package that can run to several paragraphs. Software that deals with metadata should not assume any maximum size for this field, though people shouldn’t include their instruction manual as the description.

The contents of this field can be written using reStructuredText markup [1]. For programs that work with the metadata, supporting markup is optional; programs can also display the contents of the field as-is. This means that authors should be conservative in the markup they use.


Description: This module collects votes from beagles
             in order to determine their electoral wishes.
             Do *not* try to use this module with basset hounds;
             it makes them grumpy.

Keywords (optional)

A list of additional keywords to be used to assist searching for the package in a larger catalog.


Keywords: dog puppy voting election

Home-page (optional)

A string containing the URL for the package’s home page.




A string containing the URL from which this version of the package can be downloaded. (This means that the URL can’t be something like “…/package-latest.tgz”, but instead must be “../package-0.45.tgz”.)

Author (optional)

A string containing the author’s name at a minimum; additional contact information may be provided.


Author: C. Schultz, Universal Features Syndicate,
        Los Angeles, CA <>


A string containing the author’s e-mail address. It can contain a name and e-mail address in the legal forms for a RFC 822 ‘From:’ header. It’s not optional because cataloging systems can use the e-mail portion of this field as a unique key representing the author. A catalog might provide authors the ability to store their GPG key, personal home page, and other additional metadata about the author, and optionally the ability to associate several e-mail addresses with the same person. Author-related metadata fields are not covered by this PEP.


Author-email: "C. Schultz" <>


Text indicating the license covering the package where the license is not a selection from the “License” Trove classifiers. See “Classifier” below.


License: This software may only be obtained by sending the
         author a postcard, and then the user promises not
         to redistribute it.

Classifier (multiple use)

Each entry is a string giving a single classification value for the package. Classifiers are described in PEP 301.


Classifier: Development Status :: 4 - Beta
Classifier: Environment :: Console (Text Based)

Requires (multiple use)

Each entry contains a string describing some other module or package required by this package.

The format of a requirement string is identical to that of a module or package name usable with the ‘import’ statement, optionally followed by a version declaration within parentheses.

A version declaration is a series of conditional operators and version numbers, separated by commas. Conditional operators must be one of “<”, “>”, “<=”, “>=”, “==”, and “!=”. Version numbers must be in the format accepted by the distutils.version.StrictVersion class: two or three dot-separated numeric components, with an optional “pre-release” tag on the end consisting of the letter ‘a’ or ‘b’ followed by a number. Example version numbers are “1.0”, “2.3a2”, “1.3.99”,

Any number of conditional operators can be specified, e.g. the string “>1.0, !=1.3.4, <2.0” is a legal version declaration.

All of the following are possible requirement strings: “rfc822”, “zlib (>=1.1.4)”, “zope”.

There’s no canonical list of what strings should be used; the Python community is left to choose its own standards.


Requires: re
Requires: sys
Requires: zlib
Requires: xml.parsers.expat (>1.0)
Requires: psycopg

Provides (multiple use)

Each entry contains a string describing a package or module that will be provided by this package once it is installed. These strings should match the ones used in Requirements fields. A version declaration may be supplied (without a comparison operator); the package’s version number will be implied if none is specified.


Provides: xml
Provides: xml.utils
Provides: xml.utils.iso8601
Provides: xml.dom
Provides: xmltools (1.3)

Obsoletes (multiple use)

Each entry contains a string describing a package or module that this package renders obsolete, meaning that the two packages should not be installed at the same time. Version declarations can be supplied.

The most common use of this field will be in case a package name changes, e.g. Gorgon 2.3 gets subsumed into Torqued Python 1.0. When you install Torqued Python, the Gorgon package should be removed.


Obsoletes: Gorgon

Summary of Differences From PEP 241

  • Metadata-Version is now 1.1.
  • Added the Classifiers field from PEP 301.
  • The License and Platform files should now only be used if the platform or license can’t be handled by an appropriate Classifier value.
  • Added fields: Download-URL, Requires, Provides, Obsoletes.

Open issues






Last modified: 2023-09-09 17:39:29 GMT