7. Documenting Python

The Python language has a substantial body of documentation, much of it contributed by various authors. The markup used for the Python documentation is reStructuredText, developed by the docutils project, amended by custom directives and using a toolset named Sphinx to post-process the HTML output.

This document describes the style guide for our documentation as well as the custom reStructuredText markup introduced by Sphinx to support Python documentation and how it should be used.

The documentation in HTML, PDF or EPUB format is generated from text files written using the reStructuredText format and contained in the CPython Mercurial repository.

Note

If you’re interested in contributing to Python’s documentation, there’s no need to write reStructuredText if you’re not so inclined; plain text contributions are more than welcome as well. Send an e-mail to docs@python.org or open an issue on the tracker.

7.1. 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 the documentation could be more complete or easier to use.

This document is aimed at authors and potential authors of documentation for Python. More specifically, it is for 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.

If your interest is in contributing to the Python documentation, but you don’t have the time or inclination to learn reStructuredText and the markup structures documented here, there’s a welcoming place for you among the Python contributors as well. Any time you feel that you can clarify existing documentation or provide documentation that’s missing, the existing documentation team will gladly work with you to integrate your text, dealing with the markup for you. Please don’t let the material in this document stand between the documentation and your desire to help out!

7.2. Style guide

7.2.1. Use of whitespace

All reST files use an indentation of 3 spaces; no tabs are allowed. The maximum line length is 80 characters for normal text, but tables, deeply indented code samples and long links may extend beyond that. Code example bodies should use normal Python 4-space indentation.

Make generous use of blank lines where applicable; they help grouping things together.

A sentence-ending period may be followed by one or two spaces; while reST ignores the second space, it is customarily put in by some users, for example to aid Emacs’ auto-fill mode.

7.2.2. Footnotes

Footnotes are generally discouraged, though they may be used when they are the best way to present specific information. When a footnote reference is added at the end of the sentence, it should follow the sentence-ending punctuation. The reST markup should appear something like this:

This sentence has a footnote reference. [#]_ This is the next sentence.

Footnotes should be gathered at the end of a file, or if the file is very long, at the end of a section. The docutils will automatically create backlinks to the footnote reference.

Footnotes may appear in the middle of sentences where appropriate.

7.2.3. Capitalization

In the Python documentation, the use of sentence case in section titles is preferable, but consistency within a unit is more important than following this rule. If you add a section to a chapter where most sections are in title case, you can either convert all titles to sentence case or use the dominant style in the new section title.

Sentences that start with a word for which specific rules require starting it with a lower case letter should be avoided.

Note

Sections that describe a library module often have titles in the form of “modulename — Short description of the module.” In this case, the description should be capitalized as a stand-alone sentence.

Many special names are used in the Python documentation, including the names of operating systems, programming languages, standards bodies, and the like. Most of 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.

Other terms and words deserve special mention as well; these conventions should be used to ensure consistency throughout the documentation:

CPU
For “central processing unit.” Many style guides say this should be spelled out on the first use (and if you must use it, do so!). For the Python documentation, this abbreviation should be avoided since there’s no reasonable way to predict which occurrence will be the first seen by the reader. It is better to use the word “processor” instead.
POSIX
The name assigned to a particular group of standards. This is always uppercase.
Python
The name of our favorite programming language is always capitalized.
reST
For “reStructuredText,” an easy to read, plaintext markup syntax used to produce Python documentation. When spelled out, it is always one word and both forms start with a lower case ‘r’.
Unicode
The name of a character coding system. This is always written capitalized.
Unix
The name of the operating system developed at AT&T Bell Labs in the early 1970s.

7.2.4. Affirmative Tone

The documentation focuses on affirmatively stating what the language does and how to use it effectively.

Except for certain security risks or segfault risks, the docs should avoid wording along the lines of “feature x is dangerous” or “experts only”. These kinds of value judgments belong in external blogs and wikis, not in the core documentation.

Bad example (creating worry in the mind of a reader):

Warning: failing to explicitly close a file could result in lost data or excessive resource consumption. Never rely on reference counting to automatically close a file.

Good example (establishing confident knowledge in the effective use of the language):

A best practice for using files is use a try/finally pair to explicitly close a file after it is used. Alternatively, using a with-statement can achieve the same effect. This assures that files are flushed and file descriptor resources are released in a timely manner.

7.2.5. Economy of Expression

More documentation is not necessarily better documentation. Err on the side of being succinct.

It is an unfortunate fact that making documentation longer can be an impediment to understanding and can result in even more ways to misread or misinterpret the text. Long descriptions full of corner cases and caveats can create the impression that a function is more complex or harder to use than it actually is.

7.2.6. Security Considerations (and Other Concerns)

Some modules provided with Python are inherently exposed to security issues (e.g. shell injection vulnerabilities) due to the purpose of the module (e.g. ssl). Littering the documentation of these modules with red warning boxes for problems that are due to the task at hand, rather than specifically to Python’s support for that task, doesn’t make for a good reading experience.

Instead, these security concerns should be gathered into a dedicated “Security Considerations” section within the module’s documentation, and cross-referenced from the documentation of affected interfaces with a note similar to "Please refer to the :ref:`security-considerations` section for important information on how to avoid common mistakes.".

Similarly, if there is a common error that affects many interfaces in a module (e.g. OS level pipe buffers filling up and stalling child processes), these can be documented in a “Common Errors” section and cross-referenced rather than repeated for every affected interface.

7.2.7. Code Examples

Short code examples can be a useful adjunct to understanding. Readers can often grasp a simple example more quickly than they can digest a formal description in prose.

People learn faster with concrete, motivating examples that match the context of a typical use case. For instance, the str.rpartition() method is better demonstrated with an example splitting the domain from a URL than it would be with an example of removing the last word from a line of Monty Python dialog.

The ellipsis for the sys.ps2 secondary interpreter prompt should only be used sparingly, where it is necessary to clearly differentiate between input lines and output lines. Besides contributing visual clutter, it makes it difficult for readers to cut-and-paste examples so they can experiment with variations.

7.2.8. Code Equivalents

Giving pure Python code equivalents (or approximate equivalents) can be a useful adjunct to a prose description. A documenter should carefully weigh whether the code equivalent adds value.

A good example is the code equivalent for all(). The short 4-line code equivalent is easily digested; it re-emphasizes the early-out behavior; and it clarifies the handling of the corner-case where the iterable is empty. In addition, it serves as a model for people wanting to implement a commonly requested alternative where all() would return the specific object evaluating to False whenever the function terminates early.

A more questionable example is the code for itertools.groupby(). Its code equivalent borders on being too complex to be a quick aid to understanding. Despite its complexity, the code equivalent was kept because it serves as a model to alternative implementations and because the operation of the “grouper” is more easily shown in code than in English prose.

An example of when not to use a code equivalent is for the oct() function. The exact steps in converting a number to octal doesn’t add value for a user trying to learn what the function does.

7.2.9. Audience

The tone of the tutorial (and all the docs) needs to be respectful of the reader’s intelligence. Don’t presume that the readers are stupid. Lay out the relevant information, show motivating use cases, provide glossary links, and do your best to connect-the-dots, but don’t talk down to them or waste their time.

The tutorial is meant for newcomers, many of whom will be using the tutorial to evaluate the language as a whole. The experience needs to be positive and not leave the reader with worries that something bad will happen if they make a misstep. The tutorial serves as guide for intelligent and curious readers, saving details for the how-to guides and other sources.

Be careful accepting requests for documentation changes from the rare but vocal category of reader who is looking for vindication for one of their programming errors (“I made a mistake, therefore the docs must be wrong ...”). Typically, the documentation wasn’t consulted until after the error was made. It is unfortunate, but typically no documentation edit would have saved the user from making false assumptions about the language (“I was surprised by ...”).

7.3. reStructuredText Primer

This section is a brief introduction to reStructuredText (reST) concepts and syntax, intended to provide authors with enough information to author documents productively. Since reST was designed to be a simple, unobtrusive markup language, this will not take too long.

See also

The authoritative reStructuredText User Documentation.

7.3.1. Paragraphs

The paragraph is the most basic block in a reST document. Paragraphs are simply chunks of text separated by one or more blank lines. As in Python, indentation is significant in reST, so all lines of the same paragraph must be left-aligned to the same level of indentation.

7.3.2. Inline markup

The standard reST inline markup is quite simple: use

  • one asterisk: *text* for emphasis (italics),
  • two asterisks: **text** for strong emphasis (boldface), and
  • backquotes: ``text`` for code samples.

If asterisks or backquotes appear in running text and could be confused with inline markup delimiters, they have to be escaped with a backslash.

Be aware of some restrictions of this markup:

  • it may not be nested,
  • content may not start or end with whitespace: * text* is wrong,
  • it must be separated from surrounding text by non-word characters. Use a backslash escaped space to work around that: thisis\ *one*\ word.

These restrictions may be lifted in future versions of the docutils.

reST also allows for custom “interpreted text roles”’, which signify that the enclosed text should be interpreted in a specific way. Sphinx uses this to provide semantic markup and cross-referencing of identifiers, as described in the appropriate section. The general syntax is :rolename:`content`.

7.3.3. Lists and Quotes

List markup is natural: just place an asterisk at the start of a paragraph and indent properly. The same goes for numbered lists; they can also be automatically numbered using a # sign:

* This is a bulleted list.
* It has two items, the second
  item uses two lines.

1. This is a numbered list.
2. It has two items too.

#. This is a numbered list.
#. It has two items too.

Nested lists are possible, but be aware that they must be separated from the parent list items by blank lines:

* this is
* a list

  * with a nested list
  * and some subitems

* and here the parent list continues

Definition lists are created as follows:

term (up to a line of text)
   Definition of the term, which must be indented

   and can even consist of multiple paragraphs

next term
   Description.

Paragraphs are quoted by just indenting them more than the surrounding paragraphs.

7.3.4. Source Code

Literal code blocks are introduced by ending a paragraph with the special marker ::. The literal block must be indented:

This is a normal text paragraph. The next paragraph is a code sample::

   It is not processed in any way, except
   that the indentation is removed.

   It can span multiple lines.

This is a normal text paragraph again.

The handling of the :: marker is smart:

  • If it occurs as a paragraph of its own, that paragraph is completely left out of the document.
  • If it is preceded by whitespace, the marker is removed.
  • If it is preceded by non-whitespace, the marker is replaced by a single colon.

That way, the second sentence in the above example’s first paragraph would be rendered as “The next paragraph is a code sample:”.

7.3.6. Sections

Section headers are created by underlining (and optionally overlining) the section title with a punctuation character, at least as long as the text:

=================
This is a heading
=================

Normally, there are no heading levels assigned to certain characters as the structure is determined from the succession of headings. However, for the Python documentation, here is a suggested convention:

  • # with overline, for parts
  • * with overline, for chapters
  • =, for sections
  • -, for subsections
  • ^, for subsubsections
  • ", for paragraphs

7.3.7. Explicit Markup

“Explicit markup” is used in reST for most constructs that need special handling, such as footnotes, specially-highlighted paragraphs, comments, and generic directives.

An explicit markup block begins with a line starting with .. followed by whitespace and is terminated by the next paragraph at the same level of indentation. (There needs to be a blank line between explicit markup and normal paragraphs. This may all sound a bit complicated, but it is intuitive enough when you write it.)

7.3.8. Directives

A directive is a generic block of explicit markup. Besides roles, it is one of the extension mechanisms of reST, and Sphinx makes heavy use of it.

Basically, a directive consists of a name, arguments, options and content. (Keep this terminology in mind, it is used in the next chapter describing custom directives.) Looking at this example,

.. function:: foo(x)
              foo(y, z)
   :bar: no

   Return a line of text input from the user.

function is the directive name. It is given two arguments here, the remainder of the first line and the second line, as well as one option bar (as you can see, options are given in the lines immediately following the arguments and indicated by the colons).

The directive content follows after a blank line and is indented relative to the directive start.

7.3.9. Footnotes

For footnotes, use [#]_ to mark the footnote location, and add the footnote body at the bottom of the document after a “Footnotes” rubric heading, like so:

Lorem ipsum [#]_ dolor sit amet ... [#]_

.. rubric:: Footnotes

.. [#] Text of the first footnote.
.. [#] Text of the second footnote.

You can also explicitly number the footnotes for better context.

7.3.10. Comments

Every explicit markup block which isn’t a valid markup construct (like the footnotes above) is regarded as a comment.

7.3.11. Source encoding

Since the easiest way to include special characters like em dashes or copyright signs in reST is to directly write them as Unicode characters, one has to specify an encoding:

All Python documentation source files must be in UTF-8 encoding, and the HTML documents written from them will be in that encoding as well.

7.3.12. Gotchas

There are some problems one commonly runs into while authoring reST documents:

  • Separation of inline markup: As said above, inline markup spans must be separated from the surrounding text by non-word characters, you have to use an escaped space to get around that.

7.4. Additional Markup Constructs

Sphinx adds a lot of new directives and interpreted text roles to standard reST markup. This section contains the reference material for these facilities. Documentation for “standard” reST constructs is not included here, though they are used in the Python documentation.

Note

This is just an overview of Sphinx’ extended markup capabilities; full coverage can be found in its own documentation.

7.4.1. Meta-information markup

sectionauthor

Identifies the author of the current section. The argument should include the author’s name such that it can be used for presentation (though it isn’t) and email address. The domain name portion of the address should be lower case. Example:

.. sectionauthor:: Guido van Rossum <guido@python.org>

Currently, this markup isn’t reflected in the output in any way, but it helps keep track of contributions.

7.4.2. Module-specific markup

The markup described in this section is used to provide information about a module being documented. Each module should be documented in its own file. Normally this markup appears after the title heading of that file; a typical file might start like this:

:mod:`parrot` -- Dead parrot access
===================================

.. module:: parrot
   :platform: Unix, Windows
   :synopsis: Analyze and reanimate dead parrots.
.. moduleauthor:: Eric Cleese <eric@python.invalid>
.. moduleauthor:: John Idle <john@python.invalid>

As you can see, the module-specific markup consists of two directives, the module directive and the moduleauthor directive.

module

This directive marks the beginning of the description of a module, package, or submodule. The name should be fully qualified (i.e. including the package name for submodules).

The platform option, if present, is a comma-separated list of the platforms on which the module is available (if it is available on all platforms, the option should be omitted). The keys are short identifiers; examples that are in use include “IRIX”, “Mac”, “Windows”, and “Unix”. It is important to use a key which has already been used when applicable.

The synopsis option should consist of one sentence describing the module’s purpose – it is currently only used in the Global Module Index.

The deprecated option can be given (with no value) to mark a module as deprecated; it will be designated as such in various locations then.

moduleauthor

The moduleauthor directive, which can appear multiple times, names the authors of the module code, just like sectionauthor names the author(s) of a piece of documentation. It too does not result in any output currently.

Note

It is important to make the section title of a module-describing file meaningful since that value will be inserted in the table-of-contents trees in overview files.

7.4.3. Information units

There are a number of directives used to describe specific features provided by modules. Each directive requires one or more signatures to provide basic information about what is being described, and the content should be the description. The basic version makes entries in the general index; if no index entry is desired, you can give the directive option flag :noindex:. The following example shows all of the features of this directive type:

.. function:: spam(eggs)
              ham(eggs)
   :noindex:

   Spam or ham the foo.

The signatures of object methods or data attributes should not include the class name, but be nested in a class directive. The generated files will reflect this nesting, and the target identifiers (for HTML output) will use both the class and method name, to enable consistent cross-references. If you describe methods belonging to an abstract protocol such as context managers, use a class directive with a (pseudo-)type name too to make the index entries more informative.

The directives are:

c:function

Describes a C function. The signature should be given as in C, e.g.:

.. c:function:: PyObject* PyType_GenericAlloc(PyTypeObject *type, Py_ssize_t nitems)

This is also used to describe function-like preprocessor macros. The names of the arguments should be given so they may be used in the description.

Note that you don’t have to backslash-escape asterisks in the signature, as it is not parsed by the reST inliner.

c:member

Describes a C struct member. Example signature:

.. c:member:: PyObject* PyTypeObject.tp_bases

The text of the description should include the range of values allowed, how the value should be interpreted, and whether the value can be changed. References to structure members in text should use the member role.

c:macro

Describes a “simple” C macro. Simple macros are macros which are used for code expansion, but which do not take arguments so cannot be described as functions. This is not to be used for simple constant definitions. Examples of its use in the Python documentation include PyObject_HEAD and Py_BEGIN_ALLOW_THREADS.

c:type

Describes a C type. The signature should just be the type name.

c:var

Describes a global C variable. The signature should include the type, such as:

.. cvar:: PyObject* PyClass_Type
data

Describes global data in a module, including both variables and values used as “defined constants.” Class and object attributes are not documented using this directive.

exception

Describes an exception class. The signature can, but need not include parentheses with constructor arguments.

function

Describes a module-level function. The signature should include the parameters, enclosing optional parameters in brackets. Default values can be given if it enhances clarity. For example:

.. function:: repeat([repeat=3[, number=1000000]])

Object methods are not documented using this directive. Bound object methods placed in the module namespace as part of the public interface of the module are documented using this, as they are equivalent to normal functions for most purposes.

The description should include information about the parameters required and how they are used (especially whether mutable objects passed as parameters are modified), side effects, and possible exceptions. A small example may be provided.

decorator

Describes a decorator function. The signature should not represent the signature of the actual function, but the usage as a decorator. For example, given the functions

def removename(func):
    func.__name__ = ''
    return func

def setnewname(name):
    def decorator(func):
        func.__name__ = name
        return func
    return decorator

the descriptions should look like this:

.. decorator:: removename

   Remove name of the decorated function.

.. decorator:: setnewname(name)

   Set name of the decorated function to *name*.

There is no deco role to link to a decorator that is marked up with this directive; rather, use the :func: role.

class

Describes a class. The signature can include parentheses with parameters which will be shown as the constructor arguments.

attribute

Describes an object data attribute. The description should include information about the type of the data to be expected and whether it may be changed directly. This directive should be nested in a class directive, like in this example:

.. class:: Spam

      Description of the class.

      .. data:: ham

         Description of the attribute.

If is also possible to document an attribute outside of a class directive, for example if the documentation for different attributes and methods is split in multiple sections. The class name should then be included explicitly:

.. data:: Spam.eggs
method

Describes an object method. The parameters should not include the self parameter. The description should include similar information to that described for function. This directive should be nested in a class directive, like in the example above.

decoratormethod

Same as decorator, but for decorators that are methods.

Refer to a decorator method using the :meth: role.

opcode

Describes a Python bytecode instruction.

cmdoption

Describes a Python command line option or switch. Option argument names should be enclosed in angle brackets. Example:

.. cmdoption:: -m <module>

   Run a module as a script.
envvar

Describes an environment variable that Python uses or defines.

There is also a generic version of these directives:

describe

This directive produces the same formatting as the specific ones explained above but does not create index entries or cross-referencing targets. It is used, for example, to describe the directives in this document. Example:

.. describe:: opcode

   Describes a Python bytecode instruction.

7.4.4. Showing code examples

Examples of Python source code or interactive sessions are represented using standard reST literal blocks. They are started by a :: at the end of the preceding paragraph and delimited by indentation.

Representing an interactive session requires including the prompts and output along with the Python code. No special markup is required for interactive sessions. After the last line of input or output presented, there should not be an “unused” primary prompt; this is an example of what not to do:

>>> 1 + 1
2
>>>

Syntax highlighting is handled in a smart way:

  • There is a “highlighting language” for each source file. Per default, this is 'python' as the majority of files will have to highlight Python snippets.

  • Within Python highlighting mode, interactive sessions are recognized automatically and highlighted appropriately.

  • The highlighting language can be changed using the highlightlang directive, used as follows:

    .. highlightlang:: c
    

    This language is used until the next highlightlang directive is encountered.

  • The code-block directive can be used to specify the highlight language of a single code block, e.g.:

    .. code-block:: c
    
       #include <stdio.h>
    
       void main() {
           printf("Hello world!\n");
       }
    
  • The values normally used for the highlighting language are:

    • python (the default)
    • c
    • rest
    • none (no highlighting)
  • If highlighting with the current language fails, the block is not highlighted in any way.

Longer displays of verbatim text may be included by storing the example text in an external file containing only plain text. The file may be included using the literalinclude directive. [1] For example, to include the Python source file example.py, use:

.. literalinclude:: example.py

The file name is relative to the current file’s path. Documentation-specific include files should be placed in the Doc/includes subdirectory.

7.4.5. Inline markup

As said before, Sphinx uses interpreted text roles to insert semantic markup in documents.

Names of local variables, such as function/method arguments, are an exception, they should be marked simply with *var*.

For all other roles, you have to write :rolename:`content`.

There are some additional facilities that make cross-referencing roles more versatile:

  • You may supply an explicit title and reference target, like in reST direct hyperlinks: :role:`title <target>` will refer to target, but the link text will be title.

  • If you prefix the content with !, no reference/hyperlink will be created.

  • For the Python object roles, if you prefix the content with ~, the link text will only be the last component of the target. For example, :meth:`~Queue.Queue.get` will refer to Queue.Queue.get but only display get as the link text.

    In HTML output, the link’s title attribute (that is e.g. shown as a tool-tip on mouse-hover) will always be the full target name.

The following roles refer to objects in modules and are possibly hyperlinked if a matching identifier is found:

mod

The name of a module; a dotted name may be used. This should also be used for package names.

func

The name of a Python function; dotted names may be used. The role text should not include trailing parentheses to enhance readability. The parentheses are stripped when searching for identifiers.

data

The name of a module-level variable or constant.

const

The name of a “defined” constant. This may be a C-language #define or a Python variable that is not intended to be changed.

class

A class name; a dotted name may be used.

meth

The name of a method of an object. The role text should include the type name and the method name. A dotted name may be used.

attr

The name of a data attribute of an object.

exc

The name of an exception. A dotted name may be used.

The name enclosed in this markup can include a module name and/or a class name. For example, :func:`filter` could refer to a function named filter in the current module, or the built-in function of that name. In contrast, :func:`foo.filter` clearly refers to the filter function in the foo module.

Normally, names in these roles are searched first without any further qualification, then with the current module name prepended, then with the current module and class name (if any) prepended. If you prefix the name with a dot, this order is reversed. For example, in the documentation of the codecs module, :func:`open` always refers to the built-in function, while :func:`.open` refers to codecs.open().

A similar heuristic is used to determine whether the name is an attribute of the currently documented class.

The following roles create cross-references to C-language constructs if they are defined in the API documentation:

c:data

The name of a C-language variable.

c:func

The name of a C-language function. Should include trailing parentheses.

c:macro

The name of a “simple” C macro, as defined above.

c:type

The name of a C-language type.

c:member

The name of a C type member, as defined above.

The following role does possibly create a cross-reference, but does not refer to objects:

token

The name of a grammar token (used in the reference manual to create links between production displays).

The following role creates a cross-reference to the term in the glossary:

term

Reference to a term in the glossary. The glossary is created using the glossary directive containing a definition list with terms and definitions. It does not have to be in the same file as the term markup, in fact, by default the Python docs have one global glossary in the glossary.rst file.

If you use a term that’s not explained in a glossary, you’ll get a warning during build.


The following roles don’t do anything special except formatting the text in a different style:

command

The name of an OS-level command, such as rm.

dfn

Mark the defining instance of a term in the text. (No index entries are generated.)

envvar

An environment variable. Index entries are generated.

file

The name of a file or directory. Within the contents, you can use curly braces to indicate a “variable” part, for example:

... is installed in :file:`/usr/lib/python2.{x}/site-packages` ...

In the built documentation, the x will be displayed differently to indicate that it is to be replaced by the Python minor version.

guilabel

Labels presented as part of an interactive user interface should be marked using guilabel. This includes labels from text-based interfaces such as those created using curses or other text-based libraries. Any label used in the interface should be marked with this role, including button labels, window titles, field names, menu and menu selection names, and even values in selection lists.

kbd

Mark a sequence of keystrokes. What form the key sequence takes may depend on platform- or application-specific conventions. When there are no relevant conventions, the names of modifier keys should be spelled out, to improve accessibility for new users and non-native speakers. For example, an xemacs key sequence may be marked like :kbd:`C-x C-f`, but without reference to a specific application or platform, the same sequence should be marked as :kbd:`Control-x Control-f`.

keyword

The name of a Python keyword. Using this role will generate a link to the documentation of the keyword. True, False and None do not use this role, but simple code markup (``True``), given that they’re fundamental to the language and should be known to any programmer.

mailheader

The name of an RFC 822-style mail header. This markup does not imply that the header is being used in an email message, but can be used to refer to any header of the same “style.” This is also used for headers defined by the various MIME specifications. The header name should be entered in the same way it would normally be found in practice, with the camel-casing conventions being preferred where there is more than one common usage. For example: :mailheader:`Content-Type`.

makevar

The name of a make variable.

manpage

A reference to a Unix manual page including the section, e.g. :manpage:`ls(1)`.

menuselection

Menu selections should be marked using the menuselection role. This is used to mark a complete sequence of menu selections, including selecting submenus and choosing a specific operation, or any subsequence of such a sequence. The names of individual selections should be separated by -->.

For example, to mark the selection “Start > Programs”, use this markup:

:menuselection:`Start --> Programs`

When including a selection that includes some trailing indicator, such as the ellipsis some operating systems use to indicate that the command opens a dialog, the indicator should be omitted from the selection name.

mimetype

The name of a MIME type, or a component of a MIME type (the major or minor portion, taken alone).

newsgroup

The name of a Usenet newsgroup.

option

A command-line option of Python. The leading hyphen(s) must be included. If a matching cmdoption directive exists, it is linked to. For options of other programs or scripts, use simple ``code`` markup.

program

The name of an executable program. This may differ from the file name for the executable for some platforms. In particular, the .exe (or other) extension should be omitted for Windows programs.

regexp

A regular expression. Quotes should not be included.

samp

A piece of literal text, such as code. Within the contents, you can use curly braces to indicate a “variable” part, as in :file:.

If you don’t need the “variable part” indication, use the standard ``code`` instead.

The following roles generate external links:

pep

A reference to a Python Enhancement Proposal. This generates appropriate index entries. The text “PEP number” is generated; in the HTML output, this text is a hyperlink to an online copy of the specified PEP.

rfc

A reference to an Internet Request for Comments. This generates appropriate index entries. The text “RFC number” is generated; in the HTML output, this text is a hyperlink to an online copy of the specified RFC.

Note that there are no special roles for including hyperlinks as you can use the standard reST markup for that purpose.

7.4.6. Cross-linking markup

To support cross-referencing to arbitrary sections in the documentation, the standard reST labels are “abused” a bit: Every label must precede a section title; and every label name must be unique throughout the entire documentation source.

You can then reference to these sections using the :ref:`label-name` role.

Example:

.. _my-reference-label:

Section to cross-reference
--------------------------

This is the text of the section.

It refers to the section itself, see :ref:`my-reference-label`.

The :ref: invocation is replaced with the section title.

Alternatively, you can reference any label (not just section titles) if you provide the link text :ref:`link text <reference-label>`.

7.4.7. Paragraph-level markup

These directives create short paragraphs and can be used inside information units as well as normal text:

note

An especially important bit of information about an API that a user should be aware of when using whatever bit of API the note pertains to. The content of the directive should be written in complete sentences and include all appropriate punctuation.

Example:

.. note::

   This function is not suitable for sending spam e-mails.
warning

An important bit of information about an API that a user should be aware of when using whatever bit of API the warning pertains to. The content of the directive should be written in complete sentences and include all appropriate punctuation. In the interest of not scaring users away from pages filled with warnings, this directive should only be chosen over note for information regarding the possibility of crashes, data loss, or security implications.

versionadded

This directive documents the version of Python which added the described feature, or a part of it, to the library or C API. When this applies to an entire module, it should be placed at the top of the module section before any prose.

The first argument must be given and is the version in question; if the addition is only part of the described API element, you should add a second argument consisting of a brief explanation of the change.

Example:

.. versionadded:: 3.1
   The *spam* parameter.

Note that there must be no blank line between the directive head and the explanation; this is to make these blocks visually continuous in the markup.

versionchanged

Similar to versionadded, but describes when and what changed in the named feature in some way (changed side effects, platform support, etc.). This one must have the second argument (explanation of the change).


impl-detail

This directive is used to mark CPython-specific information. Use either with a block content or a single sentence as an argument, i.e. either

.. impl-detail::

   This describes some implementation detail.

   More explanation.

or

.. impl-detail:: This shortly mentions an implementation detail.

CPython implementation detail:” is automatically prepended to the content.

seealso

Many sections include a list of references to module documentation or external documents. These lists are created using the seealso directive.

The seealso directive is typically placed in a section just before any sub-sections. For the HTML output, it is shown boxed off from the main flow of the text.

The content of the seealso directive should be a reST definition list. Example:

.. seealso::

   Module :mod:`zipfile`
      Documentation of the :mod:`zipfile` standard module.

   `GNU tar manual, Basic Tar Format <http://link>`_
      Documentation for tar archive files, including GNU tar extensions.
rubric

This directive creates a paragraph heading that is not used to create a table of contents node. It is currently used for the “Footnotes” caption.

centered

This directive creates a centered boldfaced paragraph. Use it as follows:

.. centered::

   Paragraph contents.

7.4.8. Table-of-contents markup

Since reST does not have facilities to interconnect several documents, or split documents into multiple output files, Sphinx uses a custom directive to add relations between the single files the documentation is made of, as well as tables of contents. The toctree directive is the central element.

toctree

This directive inserts a “TOC tree” at the current location, using the individual TOCs (including “sub-TOC trees”) of the files given in the directive body. A numeric maxdepth option may be given to indicate the depth of the tree; by default, all levels are included.

Consider this example (taken from the library reference index):

.. toctree::
   :maxdepth: 2

   intro
   strings
   datatypes
   numeric
   (many more files listed here)

This accomplishes two things:

  • Tables of contents from all those files are inserted, with a maximum depth of two, that means one nested heading. toctree directives in those files are also taken into account.
  • Sphinx knows that the relative order of the files intro, strings and so forth, and it knows that they are children of the shown file, the library index. From this information it generates “next chapter”, “previous chapter” and “parent chapter” links.

In the end, all files included in the build process must occur in one toctree directive; Sphinx will emit a warning if it finds a file that is not included, because that means that this file will not be reachable through standard navigation.

The special file contents.rst at the root of the source directory is the “root” of the TOC tree hierarchy; from it the “Contents” page is generated.

7.4.9. Index-generating markup

Sphinx automatically creates index entries from all information units (like functions, classes or attributes) like discussed before.

However, there is also an explicit directive available, to make the index more comprehensive and enable index entries in documents where information is not mainly contained in information units, such as the language reference.

The directive is index and contains one or more index entries. Each entry consists of a type and a value, separated by a colon.

For example:

.. index::
   single: execution; context
   module: __main__
   module: sys
   triple: module; search; path

This directive contains five entries, which will be converted to entries in the generated index which link to the exact location of the index statement (or, in case of offline media, the corresponding page number).

The possible entry types are:

single
Creates a single index entry. Can be made a subentry by separating the subentry text with a semicolon (this notation is also used below to describe what entries are created).
pair
pair: loop; statement is a shortcut that creates two index entries, namely loop; statement and statement; loop.
triple
Likewise, triple: module; search; path is a shortcut that creates three index entries, which are module; search path, search; path, module and path; module search.
module, keyword, operator, object, exception, statement, builtin
These all create two index entries. For example, module: hashlib creates the entries module; hashlib and hashlib; module. The builtin entry type is slightly different in that “built-in function” is used in place of “builtin” when creating the two entries.

For index directives containing only “single” entries, there is a shorthand notation:

.. index:: BNF, grammar, syntax, notation

This creates four index entries.

7.4.10. Grammar production displays

Special markup is available for displaying the productions of a formal grammar. The markup is simple and does not attempt to model all aspects of BNF (or any derived forms), but provides enough to allow context-free grammars to be displayed in a way that causes uses of a symbol to be rendered as hyperlinks to the definition of the symbol. There is this directive:

productionlist

This directive is used to enclose a group of productions. Each production is given on a single line and consists of a name, separated by a colon from the following definition. If the definition spans multiple lines, each continuation line must begin with a colon placed at the same column as in the first line.

Blank lines are not allowed within productionlist directive arguments.

The definition can contain token names which are marked as interpreted text (e.g. unaryneg ::= "-" `integer`) – this generates cross-references to the productions of these tokens.

Note that no further reST parsing is done in the production, so that you don’t have to escape * or | characters.

The following is an example taken from the Python Reference Manual:

.. productionlist::
   try_stmt: try1_stmt | try2_stmt
   try1_stmt: "try" ":" `suite`
            : ("except" [`expression` ["," `target`]] ":" `suite`)+
            : ["else" ":" `suite`]
            : ["finally" ":" `suite`]
   try2_stmt: "try" ":" `suite`
            : "finally" ":" `suite`

7.4.11. Substitutions

The documentation system provides three substitutions that are defined by default. They are set in the build configuration file conf.py.

|release|

Replaced by the Python release the documentation refers to. This is the full version string including alpha/beta/release candidate tags, e.g. 2.5.2b3.

|version|

Replaced by the Python version the documentation refers to. This consists only of the major and minor version parts, e.g. 2.5, even for version 2.5.1.

|today|

Replaced by either today’s date, or the date set in the build configuration file. Normally has the format April 14, 2007.

Footnotes

[1]There is a standard .. include directive, but it raises errors if the file is not found. This one only emits a warning.

7.5. Building the documentation

The toolset used to build the docs is written in Python and is called Sphinx. Sphinx is maintained separately and is not included in this tree. Also needed are docutils, supplying the base markup that Sphinx uses; Jinja, a templating engine; and optionally Pygments, a code highlighter.

To build the documentation, follow the instructions from one of the sections below. You can view the documentation after building the HTML by pointing a browser at the file Doc/build/html/index.html.

In the Python 2.7 and 3.3 branches, the Sphinx toolchain will be checked out using Subversion from svn.python.org by the Makefile. This toolchain will need an installed Python 2 to run.

In the Python 3.4 and later branches, you are expected to have installed a recent version of Sphinx on your system, so that the Makefile can find the sphinx-build command.

7.5.1. Using make / make.bat

On Unix, run the following from the root of your repository clone:

cd Doc
make html

or alternatively make -C Doc html. This builds the output as HTML.

For Windows users there is a make.bat batchfile that tries to work like make does.

Available make targets are:

  • “html”, which builds standalone HTML files for offline viewing.

  • “htmlhelp”, which builds HTML files and a HTML Help project file usable to convert them into a single Compiled HTML (.chm) file – these are popular under Microsoft Windows, but very handy on every platform.

    To create the CHM file, you need to run the Microsoft HTML Help Workshop over the generated project (.hhp) file.

  • “latex”, which builds LaTeX source files as input to “pdflatex” to produce PDF documents.

  • “text”, which builds a plain text file for each source file.

  • “linkcheck”, which checks all external references to see whether they are broken, redirected or malformed, and outputs this information to stdout as well as a plain-text (.txt) file.

  • “changes”, which builds an overview over all versionadded/versionchanged/ deprecated items in the current version. This is meant as a help for the writer of the “What’s New” document.

  • “coverage”, which builds a coverage overview for standard library modules and C API.

  • “pydoc-topics”, which builds a Python module containing a dictionary with plain text documentation for the labels defined in Doc/tools/sphinxext/pyspecific.py – pydoc needs these to show topic and keyword help.

  • “suspicious”, which checks the parsed markup for text that looks like malformed and thus unconverted reST.

7.5.2. Without make

Install the Sphinx package and its dependencies from PyPI.

Then, from the Docs directory, run

sphinx-build -b<builder> . build/<builder>

where <builder> is one of html, text, latex, or htmlhelp (for explanations see the make targets above).