Sphinx Domains

New in version 1.0.

What is a Domain?

Originally, Sphinx was conceived for a single project, the documentation of the Python language. Shortly afterwards, it was made available for everyone as a documentation tool, but the documentation of Python modules remained deeply built in – the most fundamental directives, like function, were designed for Python objects. Since Sphinx has become somewhat popular, interest developed in using it for many different purposes: C/C++ projects, JavaScript, or even reStructuredText markup (like in this documentation).

While this was always possible, it is now much easier to easily support documentation of projects using different programming languages or even ones not supported by the main Sphinx distribution, by providing a domain for every such purpose.

A domain is a collection of markup (reStructuredText directives and roles) to describe and link to objects belonging together, e.g. elements of a programming language. Directive and role names in a domain have names like domain:name, e.g. py:function. Domains can also provide custom indices (like the Python Module Index).

Having domains means that there are no naming problems when one set of documentation wants to refer to e.g. C++ and Python classes. It also means that extensions that support the documentation of whole new languages are much easier to write.

This section describes what the domains that come with Sphinx provide. The domain API is documented as well, in the section Domain API.

Basic Markup

Most domains provide a number of object description directives, used to describe specific objects 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:. An example using a Python domain directive:

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

   Spam or ham the foo.

This describes the two Python functions spam and ham. (Note that when signatures become too long, you can break them if you add a backslash to lines that are continued in the next line. Example:

.. py:function:: filterwarnings(action, message='', category=Warning, \
                                module='', lineno=0, append=False)
   :noindex:

(This example also shows how to use the :noindex: flag.)

The domains also provide roles that link back to these object descriptions. For example, to link to one of the functions described in the example above, you could say

The function :py:func:`spam` does a similar thing.

As you can see, both directive and role names contain the domain name and the directive name.

Default Domain

To avoid having to writing the domain name all the time when you e.g. only describe Python objects, a default domain can be selected with either the config value primary_domain or this directive:

.. default-domain:: name

Select a new default domain. While the primary_domain selects a global default, this only has an effect within the same file.

If no other default is selected, the Python domain (named py) is the default one, mostly for compatibility with documentation written for older versions of Sphinx.

Directives and roles that belong to the default domain can be mentioned without giving the domain name, i.e.

.. function:: pyfunc()

   Describes a Python function.

Reference to :func:`pyfunc`.

Cross-referencing syntax

For cross-reference roles provided by domains, the same facilities exist as for general cross-references. See Cross-referencing syntax.

In short:

  • You may supply an explicit title and reference target: :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.
  • If you prefix the content with ~, the link text will only be the last component of the target. For example, :py:meth:`~Queue.Queue.get` will refer to Queue.Queue.get but only display get as the link text.

The Python Domain

The Python domain (name py) provides the following directives for module declarations:

.. py:module:: name

This directive marks the beginning of the description of a module (or package submodule, in which case the name should be fully qualified, including the package name). It does not create content (like e.g. py:class does).

This directive will also cause an entry in the global module index.

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.

.. py:currentmodule:: name

This directive tells Sphinx that the classes, functions etc. documented from here are in the given module (like py:module), but it will not create index entries, an entry in the Global Module Index, or a link target for py:mod. This is helpful in situations where documentation for things in a module is spread over multiple files or sections – one location has the py:module directive, the others only py:currentmodule.

The following directives are provided for module and class contents:

.. py:function:: name(parameters)

Describes a module-level function. The signature should include the parameters as given in the Python function definition, see Python Signatures. For example:

.. py:function:: Timer.repeat(repeat=3, number=1000000)

For methods you should use py:method.

The description normally includes information about the parameters required and how they are used (especially whether mutable objects passed as parameters are modified), side effects, and possible exceptions.

This information can (in any py directive) optionally be given in a structured form, see Info field lists.

.. py:data:: name

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

.. py:exception:: name

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

.. py:class:: name
.. py:class:: name(parameters)

Describes a class. The signature can optionally include parentheses with parameters which will be shown as the constructor arguments. See also Python Signatures.

Methods and attributes belonging to the class should be placed in this directive’s body. If they are placed outside, the supplied name should contain the class name so that cross-references still work. Example:

.. py:class:: Foo

   .. py:method:: quux()

-- or --

.. py:class:: Bar

.. py:method:: Bar.quux()

The first way is the preferred one.

.. py:attribute:: name

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.

.. py:method:: name(parameters)

Describes an object method. The parameters should not include the self parameter. The description should include similar information to that described for function. See also Python Signatures and Info field lists.

.. py:staticmethod:: name(parameters)

Like py:method, but indicates that the method is a static method.

New in version 0.4.

.. py:classmethod:: name(parameters)

Like py:method, but indicates that the method is a class method.

New in version 0.6.

.. py:decorator:: name
.. py:decorator:: name(parameters)

Describes a decorator function. The signature should represent 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:

.. py:decorator:: removename

   Remove name of the decorated function.

.. py:decorator:: setnewname(name)

   Set name of the decorated function to *name*.

(as opposed to .. py:decorator:: removename(func).)

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

.. py:decoratormethod:: name
.. py:decoratormethod:: name(signature)

Same as py:decorator, but for decorators that are methods.

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

Python Signatures

Signatures of functions, methods and class constructors can be given like they would be written in Python.

Default values for optional arguments can be given (but if they contain commas, they will confuse the signature parser). Python 3-style argument annotations can also be given as well as return type annotations:

.. py:function:: compile(source : string, filename, symbol='file') -> ast object

For functions with optional parameters that don’t have default values (typically functions implemented in C extension modules without keyword argument support), you can use brackets to specify the optional parts:

compile(source[, filename[, symbol]])

It is customary to put the opening bracket before the comma.

Info field lists

New in version 0.4.

Inside Python object description directives, reST field lists with these fields are recognized and formatted nicely:

  • param, parameter, arg, argument, key, keyword: Description of a parameter.
  • type: Type of a parameter. Creates a link if possible.
  • raises, raise, except, exception: That (and when) a specific exception is raised.
  • var, ivar, cvar: Description of a variable.
  • vartype: Type of a variable. Creates a link if possible.
  • returns, return: Description of the return value.
  • rtype: Return type. Creates a link if possible.

The field names must consist of one of these keywords and an argument (except for returns and rtype, which do not need an argument). This is best explained by an example:

.. py:function:: send_message(sender, recipient, message_body, [priority=1])

   Send a message to a recipient

   :param str sender: The person sending the message
   :param str recipient: The recipient of the message
   :param str message_body: The body of the message
   :param priority: The priority of the message, can be a number 1-5
   :type priority: integer or None
   :return: the message id
   :rtype: int
   :raises ValueError: if the message_body exceeds 160 characters
   :raises TypeError: if the message_body is not a basestring

This will render like this:

send_message(sender, recipient, message_body[, priority=1])

Send a message to a recipient

Parameters:
  • sender (str) – The person sending the message
  • recipient (str) – The recipient of the message
  • message_body (str) – The body of the message
  • priority (integer or None) – The priority of the message, can be a number 1-5
Returns:

the message id

Return type:

int

Raises:
  • ValueError – if the message_body exceeds 160 characters
  • TypeError – if the message_body is not a basestring

It is also possible to combine parameter type and description, if the type is a single word, like this:

:param int priority: The priority of the message, can be a number 1-5

Cross-referencing Python objects

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

:py:mod:

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

:py:func:

Reference a Python function; dotted names may be used. The role text needs not include trailing parentheses to enhance readability; they will be added automatically by Sphinx if the add_function_parentheses config value is True (the default).

:py:data:

Reference a module-level variable.

:py:const:

Reference a “defined” constant. This may be a Python variable that is not intended to be changed.

:py:class:

Reference a class; a dotted name may be used.

:py:meth:

Reference a method of an object. The role text can include the type name and the method name; if it occurs within the description of a type, the type name can be omitted. A dotted name may be used.

:py:attr:

Reference a data attribute of an object.

:py:exc:

Reference an exception. A dotted name may be used.

:py:obj:

Reference an object of unspecified type. Useful e.g. as the default_role.

New in version 0.4.

The name enclosed in this markup can include a module name and/or a class name. For example, :py:func:`filter` could refer to a function named filter in the current module, or the built-in function of that name. In contrast, :py: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 Python’s codecs module, :py:func:`open` always refers to the built-in function, while :py:func:`.open` refers to codecs.open().

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

Also, if the name is prefixed with a dot, and no exact match is found, the target is taken as a suffix and all object names with that suffix are searched. For example, :py:meth:`.TarFile.close` references the tarfile.TarFile.close() function, even if the current module is not tarfile. Since this can get ambiguous, if there is more than one possible match, you will get a warning from Sphinx.

Note that you can combine the ~ and . prefixes: :py:meth:`~.TarFile.close` will reference the tarfile.TarFile.close() method, but the visible link caption will only be close().

The C Domain

The C domain (name c) is suited for documentation of C API.

.. c:function:: type name(signature)

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:: type name

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:: name

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 a simple C-language #define. Examples of its use in the Python documentation include PyObject_HEAD and Py_BEGIN_ALLOW_THREADS.

.. c:type:: name

Describes a C type (whether defined by a typedef or struct). The signature should just be the type name.

.. c:var:: type name

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

.. c:var:: PyObject* PyClass_Type

Cross-referencing C constructs

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

:c:data:

Reference a C-language variable.

:c:func:

Reference a C-language function. Should include trailing parentheses.

:c:macro:

Reference a “simple” C macro, as defined above.

:c:type:

Reference a C-language type.

The C++ Domain

The C++ domain (name cpp) supports documenting C++ projects.

The following directives are available. All declarations can start with a visibility statement (public, private or protected).

.. cpp:class:: class speicifer

Describe a class/struct, possibly with specification of inheritance, e.g.,:

.. cpp:class:: SomeName::SomeClass : public MyBase, MyOtherBase
.. cpp:function:: (member-)function prototype

Describe a function or member function, e.g.,:

.. cpp:function:: bool namespaced::theclass::method(int arg1, std::string arg2)

   Describes a method with parameters and types.

.. cpp:function:: bool namespaced::theclass::method(T1, T2)

   Describes a method with unnamed parameters.

.. cpp:function:: const T &array<T>::operator[]() const

   Describes the constant indexing operator of a templated array.

.. cpp:function:: operator bool() const

   Describe a casting operator here.

.. cpp:function:: constexpr void foo(std::string &bar[2]) noexcept

   Describe a constexpr function here.

.. cpp:function:: MyClass::MyClass(const MyClass&) = default

   Describe a copy constructor with default implementation.
.. cpp:member:: (member-)variable declaration
.. cpp:var:: (member-)variable declaration

Describe a varible or member variable, e.g.,:

.. cpp:member:: std::string theclass::name

.. cpp:member:: std::string theclass::name[N][M]

.. cpp:member:: int a = 42
.. cpp:type:: typedef-like declaration
.. cpp:type:: name

Describe a type as in a typedef declaration, or the name of a type with unspecified type, e.g.,:

.. cpp:type:: std::vector<int> MyList

   A typedef-like declaration of a type.

.. cpp:type:: theclass::const_iterator

   Declaration of a type alias with unspecified type.
.. cpp:enum:: unscoped enum declaration
.. cpp:enum-struct:: scoped enum declaration
.. cpp:enum-class:: scoped enum declaration

Describe a (scoped) enum, possibly with the underlying type specified. Any enumerators declared inside an unscoped enum will be declared both in the enum scope and in the parent scope. Examples:

.. cpp:enum:: MyEnum

   An unscoped enum.

.. cpp:enum:: MySpecificEnum : long

   An unscoped enum with specified underlying type.

.. cpp:enum-class:: MyScopedEnum

   A scoped enum.

.. cpp:enum-struct:: protected MyScopedVisibilityEnum : std::underlying_type<MySpecificEnum>::type

   A scoped enum with non-default visibility, and with a specified underlying type.
.. cpp:enumerator:: name
.. cpp:enumerator:: name = constant

Describe an enumerator, optionally with its value defined.

.. cpp:namespace:: namespace

Select the current namespace for the subsequent objects. Note that the namespace does not need to correspond to C++ namespaces, but can end in names of classes, e.g.,:

.. cpp:namespace:: Namespace1::Namespace2::SomeClass::AnInnerClass

All subsequent objects will be defined as if their name were declared with the namespace prepended. The subsequent cross-references will be searched for by both their specified name and with the namespace prepended.

Using NULL, 0, or nullptr as the namespace will reset it to the global namespace.

These roles link to the given object types:

:cpp:any:
:cpp:class:
:cpp:func:
:cpp:member:
:cpp:var:
:cpp:type:
:cpp:enum:
:cpp:enumerator:

Reference a C++ object by name. The name must be properly qualified relative to the position of the link.

Note

Sphinx’s syntax to give references a custom title can interfere with linking to template classes, if nothing follows the closing angle bracket, i.e. if the link looks like this: :cpp:class:`MyClass<T>`. This is interpreted as a link to T with a title of MyClass. In this case, please escape the opening angle bracket with a backslash, like this: :cpp:class:`MyClass\<T>`.

Note on References

It is currently impossible to link to a specific version of an overloaded method. Currently the C++ domain is the first domain that has basic support for overloaded methods and until there is more data for comparison we don’t want to select a bad syntax to reference a specific overload. Currently Sphinx will link to the first overloaded version of the method / function.

Note on Template Delcarations

The C++ domain currently does not support template classes/functions/aliases/variables (e.g., template<typename T> MyClass), only template instantiations (e.g., MyClass<T>).

The Standard Domain

The so-called “standard” domain collects all markup that doesn’t warrant a domain of its own. Its directives and roles are not prefixed with a domain name.

The standard domain is also where custom object descriptions, added using the add_object_type() API, are placed.

There is a set of directives allowing documenting command-line programs:

.. option:: name args, name args, ...

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

.. option:: dest_dir

   Destination directory.

.. option:: -m <module>, --module <module>

   Run a module as a script.

The directive will create cross-reference targets for the given options, referencable by option (in the example case, you’d use something like :option:`dest_dir`, :option:`-m`, or :option:`--module`).

.. envvar:: name

Describes an environment variable that the documented code or program uses or defines. Referencable by envvar.

.. program:: name

Like py:currentmodule, this directive produces no output. Instead, it serves to notify Sphinx that all following option directives document options for the program called name.

If you use program, you have to qualify the references in your option roles by the program name, so if you have the following situation

.. program:: rm

.. option:: -r

   Work recursively.

.. program:: svn

.. option:: -r revision

   Specify the revision to work upon.

then :option:`rm -r` would refer to the first option, while :option:`svn -r` would refer to the second one.

The program name may contain spaces (in case you want to document subcommands like svn add and svn commit separately).

New in version 0.5.

There is also a very generic object description directive, which is not tied to any domain:

.. describe:: text
.. object:: text

This directive produces the same formatting as the specific ones provided by domains, but does not create index entries or cross-referencing targets. Example:

.. describe:: PAPER

   You can set this variable to select a paper size.

The JavaScript Domain

The JavaScript domain (name js) provides the following directives:

.. js:function:: name(signature)

Describes a JavaScript function or method. If you want to describe arguments as optional use square brackets as documented for Python signatures.

You can use fields to give more details about arguments and their expected types, errors which may be thrown by the function, and the value being returned:

.. js:function:: $.getJSON(href, callback[, errback])

   :param string href: An URI to the location of the resource.
   :param callback: Gets called with the object.
   :param errback:
       Gets called in case the request fails. And a lot of other
       text so we need multiple lines.
   :throws SomeError: For whatever reason in that case.
   :returns: Something.

This is rendered as:

$.getJSON(href, callback[, errback])
Arguments:
  • href (string) – An URI to the location of the resource.
  • callback – Gets called with the object.
  • errback – Gets called in case the request fails. And a lot of other text so we need multiple lines.
Throws SomeError:
 

For whatever reason in that case.

Returns:

Something.

.. js:class:: name

Describes a constructor that creates an object. This is basically like a function but will show up with a class prefix:

.. js:class:: MyAnimal(name[, age])

   :param string name: The name of the animal
   :param number age: an optional age for the animal

This is rendered as:

class MyAnimal(name[, age])
Arguments:
  • name (string) – The name of the animal
  • age (number) – an optional age for the animal
.. js:data:: name

Describes a global variable or constant.

.. js:attribute:: object.name

Describes the attribute name of object.

These roles are provided to refer to the described objects:

:js:func:
:js:class:
:js:data:
:js:attr:

The reStructuredText domain

The reStructuredText domain (name rst) provides the following directives:

.. rst:directive:: name

Describes a reST directive. The name can be a single directive name or actual directive syntax (.. prefix and :: suffix) with arguments that will be rendered differently. For example:

.. rst:directive:: foo

   Foo description.

.. rst:directive:: .. bar:: baz

   Bar description.

will be rendered as:

.. foo::

Foo description.

.. bar:: baz

Bar description.

.. rst:role:: name

Describes a reST role. For example:

.. rst:role:: foo

   Foo description.

will be rendered as:

:foo:

Foo description.

These roles are provided to refer to the described objects:

:rst:dir:
:rst:role:

More domains

The sphinx-contrib repository contains more domains available as extensions; currently Ada, CoffeeScript, Erlang, HTTP, Lasso, MATLAB, PHP, and Ruby domains. Also available are domains for Common Lisp, dqn, Go, Jinja, Operation, and Scala.