\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. [Notes and questions in brackets, like this, are notes to myself while developing this document.] \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. This document is aimed at authors and potential authors of documentation for Python. Among this group, it is aimed primarily at people contributing to the standard documentation and developing additional documents using the same tools as the standard documents. This guide will be less useful for authors using the Python documentation tools for topics other than Python, and less useful still for authors not using the tools at all. The material in this guide is intended to assist authors using the Python documentation tools. It includes information on the source distribution of the standard documentation, a discussion of the Python document classes, reference material on the markup defined in the document classes, a list of the tools need for processing documents, and reference material on the tools provided with the documentation resources. At the end, there is also a section discussing future directions for the Python documentation. \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 are 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 which contains a \file{Makefile} which controls the generation of that format and provides storage for the formatted documents. The only variations within this category are 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{\LaTeX{} Syntax Primer \label{latex-primer}} [This section will discuss what the markup looks like, and explain the difference between an environment and a macro.] \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} The Python document classes define a lot of new environments and macros. This section contains the reference material for these facilities. \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{Unix} \modulesynopsis{Access to the SPAM facility of Unix.} \moduleauthor{Jane Doe}{jane.doe@frobnitz.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 any underscores, and should be the name with the underscores 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}{} 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 are supported for \var{cols} values of \code{ii}, \code{iii}, and \code{iv}. 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, typically, is an expert in the area she is writing on. The truly difficult aspects of index generation are not areas with which the documentation tools can help. However, 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}\}} Add a index entry referring to a built-in function named \var{name}; parenthesis should not be included after \var{name}. \end{macrodesc} \begin{macrodesc}{exindex}{\{\var{exception}\}} Add a reference to an exception named \var{exception}. The exception may be either string- or class-based. \end{macrodesc} \begin{macrodesc}{kwindex}{\{\var{keyword}\}} Add a reference to a language keyword (not a keyword parameter in a function or method call). \end{macrodesc} \begin{macrodesc}{obindex}{\{\var{object type}\}} Add an index entry for a built-in object type. \end{macrodesc} \begin{macrodesc}{opindex}{\{\var{operator}\}} Add a reference to an operator, such as \samp{+}. \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}\}} Add an index entry for a statement type, such as \keyword{print} or \keyword{try}/\keyword{finally}. [XXX Need better examples of difference from \macro{kwindex}. \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 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 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 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 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 is 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, grammatical errors, or this document. \end{document}