python-peps/pep-0314.txt

PEP: 314
Title: Metadata for Python Software Packages v1.1
Version: $Revision$
Last-Modified: $Date$
Author: A.M. Kuchling, Richard Jones
Status: Final
Type: Standards Track
Topic: Packaging
Content-Type: text/x-rst
Created: 12-Apr-2003
Python-Version: 2.5
Post-History: 29-Apr-2003
Replaces: 241


Introduction
============

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 setup.py files being out of sync.

The PKG-INFO file format is a single set of :rfc:`822` headers
parseable by the rfc822.py module.  The field names listed in the
following section are used as the header names.


Fields
======

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.

Metadata-Version
----------------

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

Example::

   Metadata-Version: 1.1

Name
----

The name of the package.

Example::

   Name: BeagleVote

Version
-------

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.

Example::

   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.

Example::

   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.

Example::

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

Summary
-------

A one-line summary of what the package does.

Example::

   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.

Example::

   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.

Example::

   Keywords: dog puppy voting election

Home-page (optional)
--------------------

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

Example::

   Home-page: http://www.example.com/~cschultz/bvote/

Download-URL
------------

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.

Example::

   Author: C. Schultz, Universal Features Syndicate,
           Los Angeles, CA <cschultz@peanuts.example.com>

Author-email
------------

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.

Example::

   Author-email: "C. Schultz" <cschultz@example.com>

License
-------

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

Example::

   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`.

Examples::

   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.

Example::

   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.

Example::

   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.

Example::

   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
===========

None.


Acknowledgements
================

None.


References
==========

.. [1] reStructuredText
       http://docutils.sourceforge.net/


Copyright
=========

This document has been placed in the public domain.



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