cpython/Doc/doc/doc.tex

\documentclass{howto}
\usepackage{ltxmarkup}

\title{Documenting Python}

\input{boilerplate}

% Now override the stuff that includes author information:

\author{Fred L. Drake, Jr.}
\authoraddress{
	Corporation for National Research Initiatives (CNRI) \\
	1895 Preston White Drive, Reston, Va 20191, USA \\
	E-mail: \email{fdrake@acm.org}
}
\date{\today}


\begin{document}

\maketitle

\begin{abstract}
\noindent
The Python language documentation has a substantial body of
documentation, much of it contributed by various authors.  The markup
used for the Python documentation is based on \LaTeX{} and requires a
significant set of macros written specifically for documenting Python.
Maintaining the documentation requires substantial effort, in part
because selecting the correct markup to use is not always easy.

This document describes the document classes and special markup used
in the Python documentation.  Authors may use this guide, in
conjunction with the template files provided with the
distribution, to create or maintain whole documents or sections.
\end{abstract}

\tableofcontents


\section{Introduction}

  Python's documentation has long been considered to be good for a
  free programming language.  There are a number of reasons for this,
  the most important being the early commitment of Python's creator,
  Guido van Rossum, to providing documentation on the language and its
  libraries, and the continuing involvement of the user community in
  providing assistance for creating and maintaining documentation.

  The involvement of the community takes many forms, from authoring to
  bug reports to just plain complaining when aspects of the
  documentation could be easier to use.  All of these forms of input
  from the community have proved useful during the time I've been
  involved in maintaining the documentation.

  [Who is this document for?]

  [What does it cover?]

\section{Directory Structure}

  The source distribution for the standard Python documentation
  contains a large number of directories.  While third-party documents
  do not need to be placed into this structure or need to be placed
  within a similar structure, it can be helpful to know where to look
  for examples and tools when developing new documents using the
  Python documentation tools.  This section describes this directory
  structure.

  The documentation sources are usually placed within the Python
  source distribution as the top-level subdirectory \file{Doc/}, but
  is independent of the Python source distribution.

  The \file{Doc/} directory contains a few files and several
  subdirectories.  The files are mostly self-explanatory, including a
  \file{README} and a \file{Makefile}.  The directories fall into
  three categories:

  \begin{definitions}
    \term{Document Sources}
	The \LaTeX{} sources for each document are placed in a
	separate directory.  These directories are given short,
	three-character names.

    \term{Format-Specific Output}
	Most output formats have a directory provided which contains a
	\file{Makefile} which controls the generation of that format
	and provides storage for the formatted documents.  The only
	variation within this category is the Portable Document Format
	(PDF) and PostScript versions are placed in the directories
	\file{paper-a4/} and \file{paper-letter/}.

    \term{Supplemental Files}
	Some additional directories are used to store supplemental
	files used for the various processes.  Directories are
	included for the shared \LaTeX{} document classes, the
	\LaTeX2HTML support, template files for various document
	components, and the scripts used to perform various steps in
	the formatting processes.
  \end{definitions}

\section{Document Classes}

  Two \LaTeX{} document classes are defined specifically for use with
  the Python documentation.  The \code{manual} class is for large
  documents which are sectioned into chapters, and the \code{howto}
  class is for smaller documents.

  The \code{manual} documents are larger and are used for most of the
  standard documents.  This document class is based on the standard
  \LaTeX{} \code{report} class and is formatted very much like a long
  technical report.

  The \code{howto} documents are shorter, and don't have the large
  structure of the \code{manual} documents.  This class is based on
  the standard \LaTeX{} \code{article} class and is formatted somewhat
  like the Linux Documentation Project's ``HOWTO'' series as done
  originally using the LinuxDoc software.  The original intent for the
  document class was that it serve a similar role as the LDP's HOWTO
  series, but the applicability of the class turns out to be somewhat
  more broad.  This class is used for ``how-to'' documents (this
  document is an example) and for shorter reference manuals for small,
  fairly cohesive module libraries.  Examples of the later use include
  the standard \emph{Macintosh Library Modules} and \emph{Using
  Kerberos from Python}, which contains reference material for an
  extension package.  These documents are roughly equivalent to a
  single chapter from a larger work.


\section{Python-specific Markup}

  \subsection{Information Units \label{info-units}}

    Most of the environments should be described here: \env{excdesc},
    \env{funcdesc}, etc.

    \begin{envdesc}{datadesc}{\{\var{name}\}}
    \end{envdesc}
    \begin{envdesc}{datadesc}{\{\var{name}\}}
      Like \env{datadesc}, but without creating any index entries.
    \end{envdesc}

    \begin{envdesc}{excdesc}{\{\var{name}\}}
      Describe an exception.  This may be either a string exception or
      a class exception.
    \end{envdesc}

    \begin{envdesc}{funcdesc}{\{\var{name}\}\{\var{parameter list}\}}
    \end{envdesc}
    \begin{envdesc}{funcdescni}{\{\var{name}\}\{\var{parameter list}\}}
      Like \env{funcdesc}, but without creating any index entries.
    \end{envdesc}

    \begin{envdesc}{classdesc}{\{\var{name}\}\{\var{constructor parameter list}\}}
    \end{envdesc}

    \begin{envdesc}{memberdesc}{\{\var{name}\}}
    \end{envdesc}
    \begin{envdesc}{memberdescni}{\{\var{name}\}}
      Like \env{memberdesc}, but without creating any index entries.
    \end{envdesc}

    \begin{envdesc}{methoddesc}{{[}\var{class name}{]}\{\var{name}\}\{\var{parameter list}\}}
    \end{envdesc}
    \begin{envdesc}{methoddescni}{{[}\var{class name}{]}\{\var{name}\}\{\var{parameter list}\}}
      Like \env{methoddesc}, but without creating any index entries.
    \end{envdesc}


  \subsection{Inline Markup}

    This is where to explain \macro{code}, \macro{function},
    \macro{email}, etc.


  \subsection{Module-specific Markup}

  The markup described in this section is used to provide information
  about a module being documented.  A typical use of this markup
  appears at the top of the section used to document a module.  A
  typical example might look like this:

\begin{verbatim}
\section{\module{spam} ---
         Access to the SPAM facility}

\declaremodule{extension}{spam}
  \platform{SomeOS}
\modulesynopsis{Access to the SPAM facility of SomeOS.}
\moduleauthor{John Doe}{john.doe@frobnication.org}
\end{verbatim}

  \begin{macrodesc}{declaremodule}{{[}\var{key}{]}\{\var{type}\}\{\var{name}\}}
    Requires two parameters: module type (standard, builtin,
    extension), and the module name.  An optional parameter should be
    given as the basis for the module's ``key'' used for linking to or
    referencing the section.  The ``key'' should only be given if the
    module's name contains underscores, and should be the name with the
    underscore's stripped.  This should be the first thing after the
    \macro{section} used to introduce the module.
  \end{macrodesc}

  \begin{macrodesc}{platform}{\{\var{specifier}\}}
    Specifies the portability of the module.  \var{specifier} is a
    comma-separated list of keys that specify what platforms the
    module is available on.  The keys are short identifiers;
    examples that are in use include \samp{IRIX}, \samp{Mac},
    \samp{Windows}, and \samp{Unix}.  It is important to use a key
    which has already been used when applicable.
  \end{macrodesc}

  \begin{macrodesc}{modulesynopsis}{\{\var{text}\}}
    The \var{text} is a short, ``one line'' description of the
    module that can be used as part of the chapter introduction.
    This is typically placed just after \macro{declaremodule}.
    The synopsis is used in building the contents of the table
    inserted as the \macro{localmoduletable}.  No text is
    produced at the point of the markup.
  \end{macrodesc}

  \begin{macrodesc}{moduleauthor}{\{\var{name}\}\{\var{email}\}}
    This macro is used to encode information about who authored a
    module.  This is currently not used to generate output, but can be
    used to help determine the origin of the module.
  \end{macrodesc}


  \subsection{Library-level Markup}

    This markup is used when describing a selection of modules.  For
    example, the \emph{Macintosh Library Modules} document uses this
    to help provide an overview of the modules in the collection, and
    many chapters in the \emph{Python Library Reference} use it for
    the same purpose.

  \begin{macrodesc}{localmoduletable}{}
    No parameters.  If a \file{.syn} file exists for the current
    chapter (or for the entire document in \code{howto} documents), a
    \env{synopsistable} is created with the contents loaded from the
    \file{.syn} file.
  \end{macrodesc}


  \subsection{Table Markup}

    There are three general-purpose table environments defined which
    should be used whenever possible.  These environments are defined
    to provide tables of specific widths and some convenience for
    formatting.  These environments are not meant to be general
    replacements for the standard \LaTeX{} table environments, but can
    be used for an advantage when the documents are processed using
    the tools for Python documentation processing.  In particular, the
    generated HTML looks good!  There is also an advantage for the
    eventual conversion of the documentation to SGML; see Section
    \ref{futures}, ``Future Directions.''

    Each environment is named \env{table\var{cols}}, where \var{cols}
    is the number of columns in the table specified in lower-case
    Roman numerals.  Within each of these environments, an additional
    macro, \macro{line\var{cols}}, is defined, where \var{cols}
    matches the \var{cols} value of the corresponding table
    environment.  These environments are all built on top of the
    \env{tabular} environment.

    \begin{envdesc}{tableii}{\{\var{colspec}\}\{\var{col1font}\}\{\var{heading1}\}\{\var{heading2}\}}
      Create a two-column table using the \LaTeX{} column specifier
      \var{colspec}.  The column specifier should indicate vertical
      bars between columns as appropriate for the specific table, but
      should not specify vertical bars on the outside of the table
      (that is considered a stylesheet issue).  The \var{col1font}
      parameter is used as a stylistic treatment of the first column
      of the table: the first column is presented as
      \code{\e\var{col1font}\{column1\}}.  To avoid treating the first
      column specially, \var{col1font} may be \code{textrm}.  The
      column headings are taken from the values \var{heading1} and
      \var{heading2}.
    \end{envdesc}

    \begin{macrodesc}{lineii}{\{\var{column1}\}\{\var{column2}\}}
      Create a single table row within a \env{tableii} environment.
      The text for the first column will be generated by applying the
      macro named by the \var{col1font} value when the \env{tableii}
      was opened.
    \end{macrodesc}

    \begin{envdesc}{tableiii}{\{\var{colspec}\}\{\var{col1font}\}\{\var{heading1}\}\{\var{heading2}\}\{\var{heading3}\}}
      Like the \env{tableii} environment, but with a third column.
      The heading for the third column is given by \var{heading3}.
    \end{envdesc}

    \begin{macrodesc}{lineiii}{\{\var{column1}\}\{\var{column2}\}\{\var{column3}\}}
      Like the \macro{lineii} macro, but with a third column.  The
      text for the third column is given by \var{column3}.
    \end{macrodesc}

    \begin{envdesc}{tableiv}{\{\var{colspec}\}\{\var{col1font}\}\{\var{heading1}\}\{\var{heading2}\}\{\var{heading3}\}\{\var{heading4}\}}
      Like the \env{tableiii} environment, but with a fourth column.
      The heading for the fourth column is given by \var{heading4}.
    \end{envdesc}

    \begin{macrodesc}{lineiv}{\{\var{column1}\}\{\var{column2}\}\{\var{column3}\}\{\var{column4}\}}
      Like the \macro{lineiii} macro, but with a fourth column.  The
      text for the fourth column is given by \var{column4}.
    \end{macrodesc}


    An additional table-like environment is \env{synopsistable}.  The
    table generated by this environment contains two columns, and each
    row is defined by an alternate definition of
    \macro{modulesynopsis}.  This environment is not normally use by
    the user, but is created by the \macro{localmoduletable} macro.


  \subsection{Reference List Markup \label{references}}

    Many sections include a list of references to module documentation
    or external documents.  These lists are created using the
    \env{seealso} environment.  This environment defines some
    additional macros to support creating reference entries in a
    reasonable manner.

    \begin{envdesc}{seealso}{}
      This environment creates a ``See also:'' heading and defines the
      markup used to describe individual references.
    \end{envdesc}

    \begin{macrodesc}{seemodule}{{[}\var{key}{]}\{\var{name}\}\{\var{why}\}}
      Refer to another module.  \var{why} should be a brief
      explanation of why the reference may be interesting.  The module
      name is given in \var{name}, with the link key given in
      \var{key} if necessary.  In the HTML and PDF conversions, the
      module name will be a hyperlink to the referred-to module.
    \end{macrodesc}

    \begin{macrodesc}{seetext}{\{\var{text}\}}
      Add arbitrary text \var{text} to the ``See also:'' list.  This
      can be used to refer to off-line materials or on-line materials
      using the \macro{url} macro.
    \end{macrodesc}


  \subsection{Index-generating Markup \label{indexing}}

    Effective index generation for technical documents can be very
    difficult, especially for someone familliar with the topic but not
    the creation of indexes.  Much of the difficulty arises in the
    area of terminology: including the terms an expert would use for a
    concept is not sufficient.  Coming up with the terms that a novice
    would look up is fairly difficult for an author who, hopefully, is
    an expert in the area she is writing on.

    The truly difficult aspects of index generation are not something
    which the documentation tools can help with, unfortunately.  Ease
    of producing the index once content decisions are make is within
    the scope of the tools.  Markup is provided which the processing
    software is able to use to generate a variety of kinds of index
    entry with minimal effort.  Additionally, many of the environments
    described in Section \ref{info-units}, ``Information Units,'' will
    generate appropriate entries into the general and module indexes.

    The following macro can be used to control the generation of index
    data, and should be used in the document prologue:

    \begin{macrodesc}{makemodindex}{}
      This should be used in the document prologue if a ``Module
      Index'' is desired for a document containing reference material
      on many modules.  This causes a data file
      \code{lib\macro{jobname}.idx} to be created from the
      \macro{declaremodule} macros.  This file can be processed by the
      \program{makeindex} program to generate a file which can be
      \macro{input} into the document at the desired location of the
      module index.
    \end{macrodesc}

    There are a number of macros that are useful for adding index
    entries for particular concepts, many of which are specific to
    programming languages or even Python.

    \begin{macrodesc}{bifuncindex}{\{\var{name}\}}
    \end{macrodesc}

    \begin{macrodesc}{exindex}{\{\var{exception}\}}
    \end{macrodesc}

    \begin{macrodesc}{kwindex}{\{\var{keyword}\}}
    \end{macrodesc}

    \begin{macrodesc}{obindex}{\{\var{object type}\}}
    \end{macrodesc}

    \begin{macrodesc}{opindex}{\{\var{operator}\}}
    \end{macrodesc}

    \begin{macrodesc}{refmodindex}{{[}\var{key}{]}\{\var{module}\}}
      Add an index entry for module \var{module}; if \var{module}
      contains an underscore, the optional parameter \var{key} should
      be provided as the same string with underscores removed.  An
      index entry ``\var{module} (module)'' will be generated.  This
      is intended for use with non-standard modules implemented in
      Python.
    \end{macrodesc}

    \begin{macrodesc}{refexmodindex}{{[}\var{key}{]}\{\var{module}\}}
      As for \macro{refmodindex}, but the index entry will be
      ``\var{module} (extension module).''  This is intended for use
      with non-standard modules not implemented in Python.
    \end{macrodesc}

    \begin{macrodesc}{refbimodindex}{{[}\var{key}{]}\{\var{module}\}}
      As for \macro{refmodindex}, but the index entry will be
      ``\var{module} (built-in module).''  This is intended for use
      with standard modules not implemented in Python.
    \end{macrodesc}

    \begin{macrodesc}{refstmodindex}{{[}\var{key}{]}\{\var{module}\}}
      As for \macro{refmodindex}, but the index entry will be
      ``\var{module} (standard module).''  This is intended for use
      with standard modules implemented in Python.
    \end{macrodesc}

    \begin{macrodesc}{stindex}{\{\var{statement}\}}
    \end{macrodesc}


    Additional macros are provided which are useful for conveniently
    creating general index entries which should appear at many places
    in the index by rotating a list of words.  These are simple macros
    that simply use \macro{index} to build some number of index
    entries.  Index entries build using these macros contain both
    primary and secondary text.

    \begin{macrodesc}{indexii}{\{\var{word1}\}\{\var{word2}\}}
      Build two index entries.  This is exactly equivalent to using
      \code{\e index\{\var{word1}!\var{word2}\}} and 
      \code{\e index\{\var{word2}!\var{word1}\}}.
    \end{macrodesc}

    \begin{macrodesc}{indexiii}{\{\var{word1}\}\{\var{word2}\}\{\var{word3}\}}
      Build three index entries.  This is exactly equivalent to using
      \code{\e index\{\var{word1}!\var{word2} \var{word3}\}},
      \code{\e index\{\var{word2}!\var{word3}, \var{word1}\}}, and
      \code{\e index\{\var{word3}!\var{word1} \var{word2}\}}.
    \end{macrodesc}

    \begin{macrodesc}{indexiv}{\{\var{word1}\}\{\var{word2}\}\{\var{word3}\}\{\var{word4}\}}
      Build four index entries.  This is exactly equivalent to using
      \code{\e index\{\var{word1}!\var{word2} \var{word3} \var{word4}\}},
      \code{\e index\{\var{word2}!\var{word3} \var{word4}, \var{word1}\}},
      \code{\e index\{\var{word3}!\var{word4}, \var{word1} \var{word2}\}},
      and
      \code{\e index\{\var{word4}!\var{word1} \var{word2} \var{word3}\}}.
    \end{macrodesc}


\section{Special Names}

  Many special names are used in the Python documentation, including
  the names of operating systems, programming languages, standards
  bodies, and the like.  Many of these were assigned \LaTeX{} macros
  at some point in the distant past, and these macros lived on long
  past their usefulness.  In the current markup, these entities are
  not assigned any special markup, but the preferred spellings are
  given here to aid authors in maintaining the consistency of
  presentation in the Python documentation.

  \begin{description}
    \item[POSIX]
	The name assigned to a particular group of standards.  This is
	always uppercase.

    \item[Python]
	The name of our favorite programming language is always
	capitalized.
  \end{description}


\section{Processing Tools}

  \subsection{External Tools}

    Many tools are needed to be able to process the Python
    documentation if all supported formats are required.  This
    section lists the tools used and when each is required.

    \begin{description}
      \item[\program{dvips}]
        This program is a typical part of \TeX{} installations.  It is
        used to generate PostScript from the ``device independent''
        \file{.dvi} files.  It is only needed for the conversion to
        PostScript.

      \item[\program{emacs}]
        Emacs is the kitchen sink of programmers' editors, and a damn
        fine kitchen sink it is.  It also comes with some of the
        processing needed to support the proper menu structures for
        Texinfo documents when an info conversion is desired.  This is
        only needed for the info conversion.  Using \program{xemacs}
        instead of FSF \program{emacs} may lead to instability in the
        conversion, but that's because nobody seems to maintain the
        Emacs Texinfo code in a portable manner.

      \item[\program{latex}]
        This is a world-class typesetter by Donald Knuth.  It is used
        for the conversion to PostScript, and is needed for the HTML
        conversion as well (\LaTeX2HTML requires one of the
        intermediate files it creates).

      \item[\program{latex2html}]
        Probably the longest Perl script anyone ever attempted to
        maintain.  This converts \LaTeX{} documents to HTML documents,
        and does a pretty reasonable job.  It is required for the
        conversions to HTML and GNU info.

      \item[\program{lynx}]
        This is a text-mode Web browser which includes an
        HTML-to-plain text conversion.  This is used to convert
        \code{howto} documents to text.

      \item[\program{make}]
        Just about any version should work for the standard documents,
        but GNU \program{make} is required for the experimental
        processes in \file{Doc/tools/sgmlconv/}, at least while
        they're experimental.

      \item[\program{makeindex}]
        This is a standard program for converting \LaTeX{} index data
        to a formatted index; it should be included with all \LaTeX{}
        installations.  It is needed for the PDF and PostScript
        conversions.

      \item[\program{makeinfo}]
        GNU \program{makeinfo} is used to convert Texinfo documents to
        GNU info files.  Since Texinfo is used as an intermediate
        format in the info conversion, this program is needed in that
        conversion.

      \item[\program{pdflatex}]
        pdf\TeX{} is a relatively new variant of \TeX, and is used to
        generate the PDF version of the manuals.  It is typically
        installed as part of most of the large \TeX{} distributions.
        \program{pdflatex} is PDF\TeX{} using the \LaTeX{} format.

      \item[\program{perl}]
        Perl is required for \LaTeX2HTML{} and one of the scripts used
        to post-process \LaTeX2HTML output, as well as the
        HTML-to-Texinfo conversion.  This is only required for
        the HTML and GNU info conversions.

      \item[\program{python}]
        Python is used for many of the scripts in the
        \file{Doc/tools/} directory; it is required for all
        conversions.  This shouldn't be a problem if you're interested
        in writing documentation for Python!
    \end{description}


  \subsection{Internal Tools}

    This section describes the various scripts that are used to
    implement various stages of document processing or to orchestrate
    entire build sequences.  Most of these tools are still only useful
    in the context of building the standard documentation, but some
    are more general.

    \begin{description}
      \item[\program{mkhowto}]
    \end{description}


\section{Future Directions \label{futures}}

  The history of the Python documentation is full of changes, most of
  which have been fairly small and evolutionary.  There has been a
  great deal of discussion about making large changes in the markup
  languages and tools used to process the documentation.  This section
  deals with the nature of the changes and what appears to be the most
  likely path of future development.

  \subsection{Structured Documentation \label{structured}}

    Most of the small changes to the \LaTeX{} markup have been made
    with an eye to divorcing the markup from the presentation, making
    both a bit more maintainable.  Over the course of 1998, a large
    number of changes were made with exactly this in mind; previously,
    changes had been made but in a less systematic manner and with
    more concern for not needing to update the existing content.  The
    result has been a highly structured and semantically loaded markup
    language implemented in \LaTeX.  With almost no basic \TeX{} or
    \LaTeX{} markup in use, however, the markup syntax is about the
    only evidence of \LaTeX{} in the actual document sources.

    One side effect of this is that while we've been able to use
    standard ``engines'' for manipulating the documents, such as
    \LaTeX{} and \LaTeX2HTML, most of the actual transformations have
    been created specifically for this documentation.  The \LaTeX{}
    document classes and \LaTeX2HTML support are both complete
    implementations of the specific markup designed for these
    documents.

    Combining highly customized markup with the somewhat esoteric
    systems used to process the documents leads us to ask some
    questions:  Can we do this more easily?  and, Can we do this
    better?  After a great deal of discussion with the community, we
    have determined that actively pursuing modern structured
    documentation systems worth some investment of time.

    There appear to be two real contenders in this arena: the Standard
    General Markup Language (SGML), and the Extensible Markup Language
    (XML).  Both of these standards have advantages and disadvantages,
    and many advantages are shared.

    SGML offers advantages which may appeal most to authors,
    especially those using ordinary text editors.  There are also
    additional abilities to define content models.  A number of
    high-quality tools with demonstrated maturity is available, but
    most are not free; for those which are, portability issues remain
    a problem.

    The advantages of XML include the availability of a large number
    of evolving tools.  Unfortunately, many of the associated
    standards are still evolving, and the tools will have to follow
    along.  This means that developing a robust tool set that uses
    more than the basic XML 1.0 recommendation is not possible in the
    short term.  The promised availability of a wide variety of
    high-quality tools which support some of the most important
    related standards is not immediate.  Many tools are likely to be
    free.

    [Eventual migration to SGML/XML.]

  \subsection{Discussion Forums \label{discussion}}

    Discussion of the future of the Python documentation and related
    topics takes place in the ``Doc-SIG'' special interest group.
    Information on the group, including mailing list archives and
    subscriptions, is available at
    \url{http://www.python.org/sigs/doc-sig/}.  The SIG is open to all
    interested parties.

    Comments and bug reports on the standard documents should be sent
    to \email{python-docs@python.org}.  This may include comments
    about formatting, content, or grammatical errors.

\end{document}