Epydoc Fields

Fields are used to describe specific properties of a documented object. For example, fields can be used to define the parameters and return value of a function; the instance variables of a class; and the author of a module. Each field consists of a tag, an optional argument, and a body.

1. Field Markup

Each docstring markup langauge marks fields differently. The following table shows the basic fields syntax for each markup language. For more information, see the definition of field syntax for each markup language.

Epytext reStructuredText Javadoc
@tag: body...
@tag arg: body...
:tag: body...
:tag arg: body...
@tag body...
@tag arg body...
Definition of
epytext fields
Definition of
reStructuredText fields
Definition of
Javadoc fields

2. Supported Fields

The following table lists the fields that epydoc currently recognizes. Field tags are written using epytext markup; if you are using a different markup language, then you should adjust the markup accordingly.

Functions and Methods (function or method docstrings)
@param p: ... A description of the parameter p for a function or method. It may appear in the class docstring to describe a costructor parameter: mostly useful for C extensions.
@type p: ... The expected type for the parameter. p.
@return: ... The return value for a function or method.
@rtype: ... The type of the return value for a function or method.
@keyword p: ... A description of the keyword parameter p. It may appear in the class docstring to describe a costructor keyword parameter.
@raise e: ... A description of the circumstances under which a function or method raises exception e. It may appear in the class docstring to describe an exception that can be raised by the costructor.
Variables (module, class or variable docstrings)
@ivar v: ... A description of the class instance variable v.
@cvar v: ... A description of the static class variable v.
@var v: ... A description of the module variable v.
@type v: ... The type of the variable v.
Properties (property docstrings)
@type: ... The type of the property.
Grouping and Sorting (module, class, function, or method docstrings)
@group gc1,...,cn Organizes a set of related children of a module or class into a group. g is the name of the group; and c1,...,cn are the names of the children in the group. To define multiple groups, use multiple group fields.
@sortc1,...,cn Specifies the sort order for the children of a module or class. c1,...,cn are the names of the children, in the order in which they should appear. Any children that are not included in this list will appear after the children from this list, in alphabetical order.
Related Topics
@see: ... A description of a related topic. see fields typically use documentation crossreference links or external hyperlinks that link to the related topic.
Notes and Warnings
@note: ... A note about an object. Multiple note fields may be used to list separate notes.
@attention: ... An important note about an object. Multiple attention fields may be used to list separate notes.
@bug: ... A description of a bug in an object. Multiple bug fields may be used to report separate bugs.
@warning: ... A warning about an object. Multiple warning fields may be used to report separate warnings.
Status
@version: ... The current version of an object.
@todo [ver]: ... A planned change to an object. If the optional argument ver is given, then it specifies the version for which the change will be made. Multiple todo fields may be used if multiple changes are planned.
@deprecated: ... Indicates that an object is deprecated. The body of the field describe the reason why the object is deprecated.
@since: ... The date or version when an object was first introduced.
@status: ... The current status of an object.
@change: ... A change log entry for this object.
@permission: ... The object access permission, for systems such Zope/Plone supporting this concept. It may be used more than once to specify multiple permissions.
Formal Conditions
@requires: ... A requirement for using an object. Multiple requires fields may be used if an object has multiple requirements.
@precondition: ... A condition that must be true before an object is used. Multiple precondition fields may be used if an object has multiple preconditions.
@postcondition: ... A condition that is guaranteed to be true after an object is used. Multiple postcondition fields may be used if an object has multiple postconditions.
@invariant: ... A condition which should always be true for an object. Multiple invariant fields may be used if an object has multiple invariants.
Bibliographic Information
@author: ... The author(s) of an object. Multiple author fields may be used if an object has multiple authors.
@organization: ... The organization that created or maintains an object.
@copyright: ... The copyright information for an object.
@license: ... The licensing information for an object.
@contact: ... Contact information for the author or maintainer of a module, class, function, or method. Multiple contact fields may be used if an object has multiple contacts.
Summarization
@summary: ... A summary description for an object. This description overrides the default summary (which is constructed from the first sentence of the object's description).

2.1. Notes on Supported Fields

3. Where to Write Fields

Normally the fields are written in the docstring of the documented objects: this allows you to add fields to modules, classes, function, properties. Where a docstring is not allowed, usually alternative options do exist.

3.1. Variable docstrings

Python variables don't support docstrings. The variable can be described in the module or class where it is defined using the tags @var, @ivar, @cvar; but this only allows for a textual description: no further metadata can be added to the variable (except for the type, using the @type tag.

Epydoc supports variable docstrings: if a variable assignment statement is immediately followed by a bare string literal, then that assignment is treated as a docstring for that variable. In classes, variable assignments at the class definition level are considered class variables; and assignments to instance variables in the constructor (__init__) are considered instance variables:

>>> class A:
...     x = 22
...     """Docstring for class variable A.x"""
...
...     def __init__(self, a):
...         self.y = a
...         """Docstring for instance variable A.y

Variables may also be documented using comment docstrings. If a variable assignment is immediately preceeded by a comment whose lines begin with the special marker "#:", or is followed on the same line by such a comment, then it is treated as a docstring for that variable:

>>> #: docstring for x
... x = 22
>>> x = 22 #: docstring for x

A common Python idiom is to create instance variables settings their default value in the class instead of the constructor (hopefully if the default is immutable...). To avoid Epydoc to interpret such variable as a class variable, you can describe it using the tag @ivar in the context of a variable docstring:

>>> class B:
...     y = 42
...     """@ivar: This is an instance variable."""

Notice that variable docstrings are only available for documentation when the source code is available for parsing: it is not possible to retrieve variable docstrings from introspection informations only.

3.2. C Extensions

In a C extension module, extension classes cannot have a docstring attached to the __init__ function; consequently it is not possible to document parameters and exceptions raised by the class constructor. To overcome this shortcoming, the tags @param, @keyword, @type, @exception are allowed to appear in the class docstring to refer to constructor parameters.

4. Field Synonyms

Several fields have "synonyms," or alternate tags. The following table lists all field synonyms. Field tags are written using epytext markup; if you are using a different markup language, then you should adjust the markup accordingly.

NameSynonyms
@param p: ... @parameter p: ...
@arg p: ...
@argument p: ...
@return: ... @returns: ...
@rtype: ... @returntype: ...
@raise e: ... @raises e: ...
@except e: ...
@exception e: ...
@keyword p: ... @kwarg p: ...
@kwparam p: ...
@ivar v: ... @ivariable v: ...
@cvar v: ... @cvariable v: ...
NameSynonyms
@var v: ... @variable v: ...
@see: ... @seealso: ...
@warning: ... @warn: ...
@requires: ... @require: ...
@requirement: ...
@precondition: ... @precond: ...
@postcondition: ... @postcod: ...
@organization: ... @org: ...
@copyright: ... @(c): ...
@change: ... @changed: ...

4.1. Metadata variables

Some module variables are commonly used as module metadata. Epydoc can use the value provided by these variables as alternate form for tags. The following table lists the recognized variables and the tag they replace. Customized metadata variables can be added using the method described in Adding New Fields.

TagVariable
@deprecated __deprecated__
@version __version__
@date __date__
@author
@authors
__author__
__authors__
@contact __contact__
@copyright __copyright__
@license __license__

5. Adding New Fields

New fields can be defined for the docstrings in a module using the special @newfield tag (or its synonym, @deffield). This tag has the following syntax:

@newfield tag: label [, plural]

Where tag is the new tag that's being defined; label is a string that will be used to mark this field in the generated output; and plural is the plural form of label, if different.

It will also be possibile to use the module variable __tag__ to set the value for the newly defined tag.

The following example illustrates how the @newfield can be used:

Docstring InputRendered Output
"""
@newfield corpus: Corpus, Corpora
"""

def example():
    """
    @corpus: Bob's wordlist.
    @corpus: The British National Corpus.
    """
    [...]

Corpora:

  • Bob's wordlist.
  • The British National Corpus.

Note: The module-level variable __extra_epydoc_fields__ is deprecated; use @newfield instead.

6. Markup-Specific Notes

For the most part, fields are treated identically, regardless of what markup language is used to encode them. However, there are a few minor differences, which are intended to accomodate existing standards for each markup language. In particular:

For more information about these differences, read the subsections below.

6.1. reStructuredText Fields

In reStructuredText, a single field can be used to encode the documentation for a group of related items. For example, a single :Parameters: field is often used to describe all of the parameters for a function or method:

def fox_speed(size, weight, age):
    """
    Return the maximum speed for a fox.

    :Parameters:
      - `size`: The size of the fox (in meters)
      - `weight`: The weight of the fox (in stones)
      - `age`: The age of the fox (in years)
    """
    [...]

Epydoc will automatically extract information about each parameter from this list. These consolidated fields may be written using either a bulleted list or a definition list. If a consolidated field is written as a bulleted list, then each list item must begin with the field's argument, marked as interpreted text, and followed by a colon or dash. If a consolidated field is written as a definition list, then each definition item's term should contain the field's argument, (it is not mandatory for it being marked as interpreted text). The term classifier, if present, is used to specify the associated type. The following example shows the use of a definition list to define a consolidated field. (Note that docutils requires a space before and after the ":" used to mark classifiers.)

def fox_speed(size, weight, age):
    """
    Return the maximum speed for a fox.

    :Parameters:
      size
          The size of the fox (in meters)
      weight : float
          The weight of the fox (in stones)
      age : int
          The age of the fox (in years)
    """
    [...]

The following consolidated fields are currently supported by epydoc:

Consolidated
Field Tag
Corresponding
Base Field Tag
:Parameters: :param:
:Exceptions: :except:
:Groups: :group:
:Keywords: :keyword:
Consolidated
Field Tag
Corresponding
Base Field Tag
:Variables: :var:
:Ivariables: :ivar:
:Cvariables: :cvar:
:Types: :type:

6.2. Javadoc Fields

For compatibility with Javadoc, every @see field is assumed to contain a single crossreference link, unless its body is quoted, or it starts with an HTML tag. See the Javadoc reference manual for more information about how the @see field is encoded in Javadoc.

Because Javadoc does not mark end of the optional argument, field arguments must contain exactly one word. Thus, multi-word arguments are not available in Javadoc. In particular, all group names must be single words.