python-peps/pep-0314.txt

PEP: 314
Title: Metadata for Python Software Packages v1.1
Version: $Revision$
Last-Modified: $Date$
Author: A.M. Kuchling <amk@amk.ca>, Richard Jones
Status: Draft
Type: Standards Track
Content-type: text/plain
Created: 12-Apr-2003
Python-Version: 2.3
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 [2].

      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: pyexpat (>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.  Version declarations cannot be supplied;
      instead the package's version number will be used.

      Example: 

          Provides: xml
          Provides: xml.utils
          Provides: xml.utils.iso8601
          Provides: xml.dom

    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/

    [2] PEP 301
        http://www.python.org/peps/pep-0301.html


Copyright

    This document has been placed in the public domain.



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