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>
Status: Draft
Type: Standards Track
Content-type: text/plain
Created: 12-Apr-2003
Python-Version: 2.3
Post-History: 
Replaces: 243

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.  There's no 
    extension mechanism in this simple format; the Catalog and Distutils
    SIGs will aim at getting a more flexible format ready for Python 2.2.
    

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.  The major
      supported platforms are listed below, but this list is
      necessarily incomplete.

            POSIX, MacOS, Windows, BeOS, PalmOS.

      Binary distributions 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
      are not specified in this PEP.

      Example: 

          Platform: POSIX, Windows
      
    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 one hopes that
      people won't include their instruction manual as the
      long-description.)

      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/
      
    Author (optional)

      A string containing at a minimum the author's name.  Contact
      information can also be added, separating each line with
      newlines.

      Example: 

          Author: C. Schultz
                  Universal Features Syndicate
                  Los Angeles, CA
      
    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
      
      A string selected from a short list of choices, specifying the
      license covering the package.  Some licenses result in the
      software being freely redistributable, so packagers and
      resellers can automatically know that they're free to
      redistribute the software.  Other licenses will require
      a careful reading by a human to determine how the software can be
      repackaged and resold.

      The choices are:

        Artistic, BSD, DFSG, GNU GPL, GNU LGPL, "MIT", 
        Mozilla PL, "public domain", Python, Qt PL, Zope PL, unknown,
        nocommercial, nosell, nosource, shareware, other

      Definitions of some of the licenses are:

       DFSG           The license conforms to the Debian Free Software
                      Guidelines, but does not use one of the other
                      DFSG conforming licenses listed here. 
                      More information is available at:
                      http://www.debian.org/social_contract#guidelines

       Python         Python 1.6 or higher license.  Version 1.5.2 and 
                      earlier are under the MIT license.

       public domain  Software is public domain, not copyrighted.
       unknown        Status is not known 
       nocommercial   Free private use but commercial use not permitted 
       nosell         Free use but distribution for profit by arrangement 
       nosource       Freely distributable but no source code 
       shareware      Payment is requested if software is used
       other          General category for other non-DFSG licenses 

      Some of these licenses can be interpreted to mean the software is 
      freely redistributable.  The list of redistributable licenses is:

      Artistic, BSD, DFSG, GNU GPL, GNU LGPL, "MIT", 
      Mozilla PL, "public domain", Python, Qt PL, Zope PL, 
      nosource, shareware

      Note that being redistributable does not mean a package
      qualifies as free software, 'nosource' and 'shareware' being
      examples.

      Example: 

          License: MIT

    Classifier (multiple use)

      Each entry is a string giving a single classification value
      for the package.  Classifiers are described in PEP 301 [1].

      Examples:

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

      
    Requires (multiple use)
      
      Each entry contains a string describing some other component or
      module required by this package. 

      The format of a requirement string is simple: an arbitrary
      sequence of characters, optionally followed by a version
      declaration within parentheses.  Leading and trailing whitespace
      are ignored, and whitespace within the string is normalized to a
      single space.

      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)", "XML parser".

      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: DB-API 2.0 module
       
    Provides (multiple use)

      Each entry contains a string describing a component 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 component 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

    Conflicts (multiple use)

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

      Conflict resolution probably isn't very important for Python
      programs, because few extensions will cause problems for other
      extensions, unless they happen to be using the same package
      name.  This field name is being defined here for future use.

          Conflicts: Gorgon


Summary of Differences From PEP 241

    * Metadata-Version is now 1.1.

    * Added the Classifiers field from PEP 301.

    * Added fields: Requires, Provides, Obsoletes, Conflicts.


Open issues

    With the addition of the 'Classifiers' field,  should the Platform 
    and License fields be removed?


Acknowledgements

    None yet.        


References

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


Copyright

    This document has been placed in the public domain.



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