Python Coding Conventions

Contributed code will not be refused merely because it does not strictly adhere to these conditions; as long as it's internally consistent, clean, and correct, it probably will be accepted. But don't be surprised if the "offending" code gets fiddled over time to conform to these conventions.

The Docutils project shall follow the generic coding conventions as specified in the Style Guide for Python Code and Docstring Conventions PEPs, summarized, clarified, and extended as follows:

• 4 spaces per indentation level. No hard tabs.
• Use only 7-bit ASCII, no 8-bit strings. See Docutils Internationalization.
• No one-liner compound statements (i.e., no if x: return: use two lines & indentation), except for degenerate class or method definitions (i.e., class X: pass is OK.).
• Lines should be no more than 78 characters long.
• Use "StudlyCaps" for class names (except for element classes in docutils.nodes).
• Use "lowercase" or "lowercase_with_underscores" for function, method, and variable names. For short names, maximum two words, joined lowercase may be used (e.g. "tagname"). For long names with three or more words, or where it's hard to parse the split between two words, use lowercase_with_underscores (e.g., "note_explicit_target", "explicit_target"). If in doubt, use underscores.
• Avoid lambda expressions, which are inherently difficult to understand. Named functions are preferable and superior: they're faster (no run-time compilation), and well-chosen names serve to document and aid understanding.
• Avoid functional constructs (filter, map, etc.). Use list comprehensions instead.
• Avoid from __future__ import constructs. They are inappropriate for production code.
• Use 'single quotes' for string literals, and """triple double quotes""" for docstrings.

Documentation Conventions

• Docutils documentation is written using reStructuredText, of course.

• Use 7-bit ASCII if at all possible, and Unicode substitutions when necessary.

• Use the following section title adornment styles:

  ================
   Document Title
  ================
  
  --------------------------------------------
   Document Subtitle, or Major Division Title
  --------------------------------------------
  
  Section
  =======
  
  Subsection
  ----------
  
  Sub-Subsection
  ``````````````
  
  Sub-Sub-Subsection
  ..................
  

• Use two blank lines before each section/subsection/etc. title. One blank line is sufficient between immediately adjacent titles.

• Add a bibliographic field list immediately after the document title/subtitle. See the beginning of this document for an example.

• Add an Emacs "local variables" block in a comment at the end of the document. See the end of this document for an example.

Copyrights and Licensing

The majority of the Docutils project code and documentation has been placed in the public domain. Unless clearly and explicitly indicated otherwise, any patches (modifications to existing files) submitted to the project for inclusion (via Subversion, SourceForge trackers, mailing lists, or private email) are assumed to be in the public domain as well.

Any new files contributed to the project should clearly state their intentions regarding copyright, in one of the following ways:

• Public domain (preferred): include the statement "This module/document has been placed in the public domain."
• Copyright & open source license: include a copyright notice, along with either an embedded license statement, a reference to an accompanying license file, or a license URL.

One of the goals of the Docutils project, once complete, is to be incorporated into the Python standard library. At that time copyright of the Docutils code will be assumed by or transferred to the Python Software Foundation (PSF), and will be released under Python's license. If the copyright/license option is chosen for new files, the license should be compatible with Python's current license, and the author(s) of the files should be willing to assign copyright to the PSF. The PSF accepts the Academic Free License v. 2.1 and the Apache License, Version 2.0.

Subversion Repository

Please see the repository documentation for details on how to access Docutils' Subversion repository. Anyone can access the repository anonymously. Only project developers can make changes. (If you would like to become a project developer, just ask!) Also see Setting Up For Docutils Development below for some useful info.

Unless you really really know what you're doing, please do not use svn import. It's quite easy to mess up the repository with an import.

Version Numbering

Docutils version numbering uses a major.minor.micro scheme (x.y.z; for example, 0.4.1).

Major releases (x.0, e.g. 1.0) will be rare, and will represent major changes in API, functionality, or commitment. For example, as long as the major version of Docutils is 0, it is to be considered experimental code. When Docutils reaches version 1.0, the major APIs will be considered frozen and backward compatibility will become of paramount importance.

Releases that change the minor number (x.y, e.g. 0.5) will be feature releases; new features from the Docutils core will be included.

Releases that change the micro number (x.y.z, e.g. 0.4.1) will be bug-fix releases. No new features will be introduced in these releases; only bug fixes off of maintenance branches will be included.

This policy was adopted in October 2005, and will take effect with Docutils version 0.4. Prior to version 0.4, Docutils didn't have an official version numbering policy, and micro releases contained both bug fixes and new features.

Snapshots

Snapshot tarballs will be generated regularly from

• the Docutils core, representing the current cutting-edge state of development;
• each active maintenance branch, for bug fixes;
• each development branch, representing the unstable seat-of-your-pants bleeding edge.

The sandbox/infrastructure/docutils-update shell script, run as an hourly cron job on the BerliOS server, is responsible for automatically generating the snapshots and updating the web site. See the web site docs.

Setting Up For Docutils Development

When making changes to the code, testing is a must. The code should be run to verify that it produces the expected results, and the entire test suite should be run too. The modified Docutils code has to be accessible to Python for the tests to have any meaning. There are two ways to keep the Docutils code accessible during development:

1. Update your PYTHONPATH environment variable so that Python picks up your local working copy of the code. This is the recommended method.

   We'll assume that the Docutils trunk is checked out under your ~/projects/ directory as follows:

   svn co svn+ssh://<user>@svn.berlios.de/svnroot/repos/docutils/trunk \
       docutils
   

   For the bash shell, add this to your ~/.profile:

   PYTHONPATH=$HOME/projects/docutils/docutils
   PYTHONPATH=$PYTHONPATH:$HOME/projects/docutils/docutils/extras
   export PYTHONPATH
   

   The first line points to the directory containing the docutils package. The second line adds the directory containing the third-party modules Docutils depends on. The third line exports this environment variable. You may also wish to add the tools directory to your PATH:

   PATH=$PATH:$HOME/projects/docutils/docutils/tools
   export PATH
   

2. Before you run anything, every time you make a change, reinstall Docutils:

   python setup.py install
   

   Caution!

   This method is not recommended for day-to-day development; it's too easy to forget. Confusion inevitably ensues.

   If you install Docutils this way, Python will always pick up the last-installed copy of the code. If you ever forget to reinstall the "docutils" package, Python won't see your latest changes.

A useful addition to the docutils top-level directory in branches and alternate copies of the code is a set-PATHS file containing the following lines:

# source this file
export PYTHONPATH=$PWD:$PWD/extras
export PATH=$PWD/tools:$PATH

Open a shell for this branch, cd to the docutils top-level directory, and "source" this file. For example, using the bash shell:

$ cd some-branch/docutils
$ . set-PATHS

Mailing Lists

Developers are recommended to subscribe to all Docutils mailing lists.

The Wiki

There is a development wiki at http://docutils.python-hosting.com/ as a scratchpad for transient notes. Please use the repository for permament document storage.

The Sandbox

The sandbox directory is a place to play around, to try out and share ideas. It's a part of the Subversion repository but it isn't distributed as part of Docutils releases. Feel free to check in code to the sandbox; that way people can try it out but you won't have to worry about it working 100% error-free, as is the goal of the Docutils core. Each developer who wants to play in the sandbox should create either a project-specific subdirectory or personal subdirectory (suggested name: SourceForge ID, nickname, or given name + family initial). It's OK to make a mess in your personal space! But please, play nice.

Please update the sandbox README file with links and a brief description of your work.

In order to minimize the work necessary for others to install and try out new, experimental components, the following sandbox directory structure is recommended:

sandbox/
    project_name/ # For a collaborative project.
                  # Structure as in userid/component_name below.
    userid/       # For personal space.
        component_name/ # A verbose name is best.
            README.txt  # Please explain the requirements,
                        # purpose/goals, and usage.
            docs/
                ...
            component.py    # The component is a single module.
                        # *OR* (but *not* both)
            component/  # The component is a package.
                __init__.py  # Contains the Reader/Writer class.
                other1.py    # Other modules and data files used
                data.txt     # by this component.
                ...
            test/       # Test suite.
                ...
            tools/      # For front ends etc.
                ...
            setup.py    # Use Distutils to install the component
                        # code and tools/ files into the right
                        # places in Docutils.

Some sandbox projects are destined to become Docutils components once completed. Others, such as add-ons to Docutils or applications of Docutils, graduate to become parallel projects.

Parallel Projects

Parallel projects contain useful code that is not central to the functioning of Docutils. Examples are specialized add-ons or plug-ins, and applications of Docutils. They use Docutils, but Docutils does not require their presence to function.

An official parallel project will have its own directory beside (or parallel to) the main docutils directory in the Subversion repository. It can have its own web page in the docutils.sourceforge.net domain, its own file releases and downloadable snapshots, and even a mailing list if that proves useful. However, an official parallel project has implications: it is expected to be maintained and continue to work with changes to the core Docutils.

A parallel project requires a project leader, who must commit to coordinate and maintain the implementation:

• Answer questions from users and developers.
• Review suggestions, bug reports, and patches.
• Monitor changes and ensure the quality of the code and documentation.
• Coordinate with Docutils to ensure interoperability.
• Put together official project releases.

Of course, related projects may be created independently of Docutils. The advantage of a parallel project is that the SourceForge environment and the developer and user communities are already established. Core Docutils developers are available for consultation and may contribute to the parallel project. It's easier to keep the projects in sync when there are changes made to the core Docutils code.