The Epytext Markup Language
===========================

.. $Id: manual-epytext.txt 1547 2007-02-21 17:34:54Z dvarrazzo $

A Brief Introduction
--------------------

Epytext is a simple lightweight markup language that lets you add formatting
and structue to docstrings. Epydoc uses that formatting and structure to
produce nicely formatted API documentation. The following example (which has
an unusually high ratio of documentaiton to code) illustrates some of the
basic features of epytext:

.. python::

    def x_intercept(m, b):
        """
        Return the x intercept of the line M{y=m*x+b}.  The X{x intercept}
        of a line is the point at which it crosses the x axis (M{y=0}).

        This function can be used in conjuction with L{z_transform} to
        find an arbitrary function's zeros.

        @type  m: number
        @param m: The slope of the line.
        @type  b: number
        @param b: The y intercept of the line.  The X{y intercept} of a
                  line is the point at which it crosses the y axis (M{x=0}).
        @rtype:   number
        @return:  the x intercept of the line M{y=m*x+b}.
        """
	return -b/m

You can compare this function definition with the `API documentation`__
generated by epydoc. Note that:

* Paragraphs are separated by blank lines.
* Inline markup has the form "*x*\ ``{``\ ...\ ``}``", where "*x*" is a 
  single capital letter. This example uses inline markup to mark mathematical 
  expressions ("``M{...}``"); terms that should be indexed ("``X{...}``"); 
  and links to the documentation of other objects ("``L{...}``").
* Descriptions of parameters, return values, and types are marked with 
  "``@``\ *field*\ ``:``" or "``@``\ *field arg*\ ``:``", where "*field*" 
  identifies the kind of description, and "*arg*" specifies what object is 
  described.

.. __: http://epydoc.sourceforge.net/
       examples/epytext_example-module.html#x_intercept

Epytext is intentionally very lightweight. If you wish to use a more
expressive markup language, I recommend reStructuredText_.


Epytext Language Overview
-------------------------

Epytext is a lightweight markup language for Python docstrings. The epytext
markup language is used by epydoc to parse docstrings and create structured API
documentation. Epytext markup is broken up into the following categories:

* **Block Structure** divides the docstring into nested blocks of text, such
  as *paragraphs* and *lists*.

    o **Basic Blocks** are the basic unit of block structure.

    o **Hierarchical blocks** represent the nesting structure of the docstring.

* **Inline Markup** marks regions of text within a basic block with properties,
  such as italics and hyperlinks.


Block Structure
---------------

Block structure is encoded using indentation, blank lines, and a handful of
special character sequences.

* Indentation is used to encode the nesting structure of hierarchical blocks.
  The indentation of a line is defined as the number of leading spaces on that
  line; and the indentation of a block is typically the indentation of its
  first line.
* Blank lines are used to separate blocks. A blank line is a line that only
  contains whitespace.
* Special character sequences are used to mark the beginnings of some blocks.
  For example, '``-``' is used as a bullet for unordered list items, and
  '``>>>``' is used to mark `doctest blocks`_.

The following sections describe how to use each type of block structure.


Paragraphs
''''''''''

A paragraph is the simplest type of basic block. It consists of one or more
lines of text. Paragraphs must be left justified (i.e., every line must have
the same indentation). The following example illustrates how paragraphs can be
used:

.. list-table::
   :header-rows: 1

   *  - Docstring Input
      - Rendered Output

   *  - .. python::

            def example():
                """
                This is a paragraph.  Paragraphs can
                span multiple lines, and can contain
                I{inline markup}.

                This is another paragraph.  Paragraphs
                are separated by blank lines.
                """
                *[...]*

      - This is a paragraph. Paragraphs can span multiple lines,
        and contain *inline markup*.

        This is another paragraph. Paragraphs are separated from each
        other by blank lines.

Lists
'''''

Epytext supports both ordered and unordered lists. A list consists of one or
more consecutive *list items* of the same type (ordered or unordered), with the
same indentation. Each list item is marked by a *bullet*. The bullet for
unordered list items is a single dash character (``-``). Bullets for ordered
list items consist of a series of numbers followed by periods, such as
``12.`` or ``1.2.8.``.

List items typically consist of a bullet followed by a space and a single
paragraph. The paragraph may be indented more than the list item's bullet;
often, the paragraph is intended two or three characters, so that its left
margin lines up with the right side of the bullet. The following example
illustrates a simple ordered list.


.. list-table::
   :header-rows: 1

   * - Docstring Input
     - Rendered Output

   * - .. python::

            def example():
                """
                1. This is an ordered list item.

                2. This is a another ordered list
                item.

                3. This is a third list item.  Note that
                   the paragraph may be indented more
                   than the bullet.
                """
                *[...]*

     -  1. This is an ordered list item.
        2. This is another ordered list item.
        3. This is a third list item. Note that the paragraph may be
           indented more than the bullet.

List items can contain more than one paragraph; and they can also contain
sublists, `literal blocks`, and `doctest blocks`. All of the blocks contained
by a list item must all have equal indentation, and that indentation must be
greater than or equal to the indentation of the list item's bullet. If the
first contained block is a paragraph, it may appear on the same line as the
bullet, separated from the bullet by one or more spaces, as shown in the
previous example. All other block types must follow on separate lines.

Every list must be separated from surrounding blocks by indentation:


.. list-table::
   :header-rows: 1

   * - Docstring Input
     - Rendered Output

   * - .. python::

            def example():
                """
                This is a paragraph.
                  1. This is a list item.
                  2. This a second list
                     item.
                       - This is a sublist
                """
                [...]

     - This is a paragraph.

       1. This is a list item.
       2. This is a second list item.

          * This is a sublist.

Note that sublists must be separated from the blocks in their parent list
item by indentation. In particular, the following docstring generates an error,
since the sublist is not separated from the paragraph in its parent list item
by indentation:

.. list-table::
   :header-rows: 1

   * - Docstring Input
     - Rendered Output

   * - .. python::

            def example():
                """
                1. This is a list item.  Its
                paragraph is indented 7 spaces.
                - This is a sublist.  It is
                  indented 7 spaces.
                """
                #[...]

     - **L5: Error: Lists must be indented.**

The following example illustrates how lists can be used:

.. list-table::
   :header-rows: 1

   * - Docstring Input
     - Rendered Output

   * - .. python::

        def example():
            """
            This is a paragraph.
              1. This is a list item.
                - This is a sublist.
                - The sublist contains two
                  items.
                    - The second item of the
                      sublist has its own sublist.

              2. This list item contains two
                 paragraphs and a doctest block.

                 >>> print 'This is a doctest block'
                 This is a doctest block

                 This is the second paragraph.
            """
            #[...]

     - This is a paragraph.

       1. This is a list item.

          * This is a sublist.
          * The sublist contains two items.

            - The second item of the sublist has its own own sublist.

       2. This list item contains two paragraphs and a doctest block.

          >>> print 'This is a doctest block'
          This is a doctest block

          This is the second paragraph.

Epytext will treat any line that begins with a bullet as a list item. If you
want to include bullet-like text in a paragraph, then you must either ensure
that it is not at the beginning of the line, or use escaping_ to prevent
epytext from treating it as markup:

.. list-table::
   :header-rows: 1

   * - Docstring Input
     - Rendered Output

   * - .. python::

        def example():
            """
            This sentence ends with the number
            1.  Epytext can't tell if the "1."
            is a bullet or part of the paragraph,
            so it generates an error.
            """
            #[...]

     - **L4: Error: Lists must be indented.**

   * - .. python::

        def example():
            """
            This sentence ends with the number 1.

            This sentence ends with the number
            E{1}.
            """
            #[...]

     - This sentence ends with the number 1.

       This sentence ends with the number 1.


Sections
''''''''

A section consists of a heading followed by one or more child blocks.

* The heading is a single underlined line of text. Top-level section headings
  are underlined with the '``=``' character; subsection headings are
  underlined with the '``-``' character; and subsubsection headings are
  underlined with the '``~``' character. The length of the underline must
  exactly match the length of the heading.
* The child blocks can be paragraphs, lists, literal blocks, doctest blocks,
  or sections. Each child must have equal indentation, and that indentation
  must be greater than or equal to the heading's indentation.

The following example illustrates how sections can be used:


.. list-table::
   :header-rows: 1

   * - Docstring Input
     - Rendered Output

   * - .. python::

        def example():
            """
            This paragraph is not in any section.

            Section 1
            =========
              This is a paragraph in section 1.

              Section 1.1
              -----------
              This is a paragraph in section 1.1.

            Section 2
            =========
              This is a paragraph in section 2.
            """
            #[...]

     - 
        .. class:: h1

            Section 1

        This is a paragraph in section 1.

        .. class:: h2

            Section 1.1

        This is a paragraph in section 1.1.

        .. class:: h1

            Section 2

        This is a paragraph in section 2.


Literal Blocks
''''''''''''''

Literal blocks are used to represent "preformatted" text. Everything within a
literal block should be displayed exactly as it appears in plaintext. In
particular:

* Spaces and newlines are preserved.
* Text is shown in a monospaced font.
* Inline markup is not detected.

Literal blocks are introduced by paragraphs ending in the special sequence
"``::``". Literal blocks end at the first line whose indentation is equal to
or less than that of the paragraph that introduces them. The following example
shows how literal blocks can be used:


.. list-table::
   :header-rows: 1

   * - Docstring Input
     - Rendered Output

   * - .. python::

        def example():
            """
            The following is a literal block::

                Literal /
                       / Block

            This is a paragraph following the
            literal block.
            """
            #[...]

     - The following is a literal block::

            Literal /
                   / Block

       This is a paragraph following the literal block.

Literal blocks are indented relative to the paragraphs that introduce them;
for example, in the previous example, the word "Literal" is displayed with four
leading spaces, not eight. Also, note that the double colon ("``::``") that
introduces the literal block is rendered as a single colon.


Doctest Blocks
''''''''''''''

Doctest blocks contain examples consisting of Python expressions and their
output. Doctest blocks can be used by the doctest module to test the
documented object. Doctest blocks begin with the special sequence
"``>>>``". Doctest blocks are delimited from surrounding blocks by blank lines.
Doctest blocks may not contain blank lines. The following example shows how
doctest blocks can be used:


.. list-table::
   :header-rows: 1

   * - Docstring Input
     - Rendered Output

   * - .. python::

        def example():
            """
            The following is a doctest block:

                >>> print (1+3,
                ...        3+5)
                (4, 8)
                >>> 'a-b-c-d-e'.split('-')
                ['a', 'b', 'c', 'd', 'e']

            This is a paragraph following the
            doctest block.
            """
            #[...]

     - The following is a doctest block:

       >>> print (1+3,
       ...        3+5)
       (4, 8)
       >>> 'a-b-c-d-e'.split('-')
       ['a', 'b', 'c', 'd', 'e']

       This is a paragraph following the doctest block.


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 is marked by a *field tag*, which consist of an at sign ('``@``')
followed by a *field name*, optionally followed by a space and a *field
argument*, followed by a colon ('``:``'). For example, '``@return:``' and
'``@param x:``' are field tags.

Fields can contain paragraphs, lists, literal blocks, and doctest blocks.
All of the blocks contained by a field must all have equal indentation, and
that indentation must be greater than or equal to the indentation of the
field's tag. If the first contained block is a paragraph, it may appear on the
same line as the field tag, separated from the field tag by one or more spaces.
All other block types must follow on separate lines.

Fields must be placed at the end of the docstring, after the description of
the object. Fields may be included in any order.

Fields do not need to be separated from other blocks by a blank line. Any line
that begins with a field tag followed by a space or newline is considered a
field.

The following example illustrates how fields can be used:

.. list-table::
   :header-rows: 1

   * - Docstring Input
     - Rendered Output

   * - .. python::

        def example():
            """
            @param x: This is a description of
                the parameter x to a function.
                Note that the description is
                indented four spaces.
            @type x: This is a description of
                x's type.
            @return: This is a description of
                the function's return value.

                It contains two paragraphs.
            """
            #[...]

     -  **Parameters:**
            **x** - This is a description of the parameter x to a function.
            Note that the description is indented four spaces.

                *(type=This is a description of x's type.)*

        **Returns:**
            This is a description of the function's return value.

            It contains two paragraphs.

For a list of the fields that are supported by epydoc, see the `epydoc fields`
chapter.


Inline Markup
-------------

Inline markup has the form '``x{...}``', where ``x`` is a single capital letter
that specifies how the text between the braces should be rendered. Inline
markup is recognized within paragraphs and section headings. It is *not*
recognized within literal and doctest blocks. Inline markup can contain
multiple words, and can span multiple lines. Inline markup may be nested.

A matching pair of curly braces is only interpreted as inline markup if the
left brace is immediately preceeded by a capital letter. So in most cases, you
can use curly braces in your text without any form of escaping. However, you do
need to escape curly braces when:

1. You want to include a single (un-matched) curly brace.
2. You want to preceed a matched pair of curly braces with a capital letter.

Note that there is no valid Python expression where a pair of matched curly
braces is immediately preceeded by a capital letter (except within string
literals). In particular, you never need to escape braces when writing Python
dictionaries. See also escaping_.


Basic Inline Markup
'''''''''''''''''''

 Epytext defines four types of inline markup that specify how text should be
 displayed:

* ``I{...}``: Italicized text.
* ``B{...}``: Bold-faced text.
* ``C{...}``: Source code or a Python identifier.
* ``M{...}``: A mathematical expression.

By default, source code is rendered in a fixed width font; and mathematical
expressions are rendered in italics. But those defaults may be changed by
modifying the CSS stylesheet. The following example illustrates how the four
basic markup types can be used:

.. list-table::
   :header-rows: 1

   * - Docstring Input
     - Rendered Output

   * - .. python::

        def example():
            """
            I{B{Inline markup} may be nested; and
            it may span} multiple lines.

              - I{Italicized text}
              - B{Bold-faced text}
              - C{Source code}
              - M{Math}

            Without the capital letter, matching
            braces are not interpreted as markup:
            C{my_dict={1:2, 3:4}}.
            """
            #[...]

     -  **Inline markup** *may be nested*; and it may span  multiple lines.

        - *Italicized text*
        - **Bold-faced text**
        - ``Source code``
        - Math: *m*x+b*

        Without the capital letter, matching braces are not interpreted as
        markup: ``my_dict={1:2, 3:4}``.


URLs
''''

The inline markup construct ``U{``\ *text<url>*\ ``}`` is used to create links
to external URLs and URIs. '*text*' is the text that should be displayed for
the link, and '*url*' is the target of the link. If you wish to use the URL as
the text for the link, you can simply write "``U{``\ *url*\ ``}``". Whitespace
within URL targets is ignored. In particular, URL targets may be split over
multiple lines. The following example illustrates how URLs can be used:

.. list-table::
   :header-rows: 1

   * - Docstring Input
     - Rendered Output

   * - .. python::
   
        def example():
            """
            - U{www.python.org}
            - U{http://www.python.org}
            - U{The epydoc homepage<http://
            epydoc.sourceforge.net>}
            - U{The B{Python} homepage
            <www.python.org>}
            - U{Edward Loper<mailto:edloper@
            gradient.cis.upenn.edu>}
            """
            #[...]

     -  * `www.python.org`_
        * http://www.python.org
        * `The epydoc homepage`_
        * |pyhome|__
        * `Edward Loper <mailto:edloper@gradient.cis.upenn.edu>`__

        .. __: http://www.python.org
        .. _The epydoc homepage: http://epydoc.sourceforge.net
        .. _www.python.org: http://www.python.org
        .. |pyhome| replace:: The **Python** homepage


Documentation Crossreference Links
''''''''''''''''''''''''''''''''''

The inline markup construct '``L{``\ *text<object>*\ ``}``' is used to create
links to the documentation for other Python objects. '*text*' is the text that
should be displayed for the link, and '*object*' is the name of the Python
object that should be linked to. If you wish to use the name of the Python
object as the text for the link, you can simply write ``L{``\ *object*\ }``.
Whitespace within object names is ignored. In particular, object names may be
split over multiple lines. The following example illustrates how documentation
crossreference links can be used:

.. list-table::
   :header-rows: 1

   * - Docstring Input
     - Rendered Output

   * - .. python::

        def example():
            """
            - L{x_transform}
            - L{search<re.search>}
            - L{The I{x-transform} function
            <x_transform>}
            """
            #[...]

     - * `x_transform`_
       * `search`_
       * `The x-transform function`_

       .. _x_transform: http://www.example.com
       .. _search: http://www.example.com
       .. _The x-transform function: http://www.example.com

In order to find the object that corresponds to a given name, epydoc checks the
following locations, in order:

1. If the link is made from a class or method docstring, then epydoc checks for
   a method, instance variable, or class variable with the given name.
2. Next, epydoc looks for an object with the given name in the current module.
3. Epydoc then tries to import the given name as a module. If the current
   module is contained in a package, then epydoc will also try importing the
   given name from all packages containing the current module.
4. Epydoc then tries to divide the given name into a module name and an
   object name, and to import the object from the module. If the current module
   is contained in a package, then epydoc will also try importing the module
   name from all packages containing the current module.
5. Finally, epydoc looks for a class name in any module with the given name.
   This is only returned if there is a single class with such name.

If no object is found that corresponds with the given name, then epydoc
issues a warning.


Indexed Terms
'''''''''''''

Epydoc automatically creates an index of term definitions for the API
documentation. The inline markup construct '``X{...}``' is used to mark terms
for inclusion in the index. The term itself will be italicized; and a link will
be created from the index page to the location of the term in the text. The
following example illustrates how index terms can be used:

.. list-table::
   :header-rows: 1

   * - Docstring Input
     - Rendered Output

   * - .. python::

        def example():
            """
            An X{index term} is a term that
            should be included in the index.
            """
            #[...]

     -  An *index term* is a term that should be included in the index.
   
            ============ ==============
                      Index
            ===========================
            index term   *example*
            x intercept  *x_intercept*
            y intercept  *x_intercept*
            ============ ==============


Symbols
'''''''

Symbols are used to insert special characters in your documentation. A symbol
has the form '``S{code}``', where code is a symbol code that specifies what
character should be produced. The following example illustrates how symbols can
be used to generate special characters:

.. include:: <xhtml1-symbol.txt>

.. list-table::
   :header-rows: 1

   * - Docstring Input
     - Rendered Output

   * - .. python::

        def example():
            """
            Symbols can be used in equations:

              - S{sum}S{alpha}/x S{<=} S{beta}

            S{<-} and S{larr} both give left
            arrows.  Some other arrows are
            S{rarr}, S{uarr}, and S{darr}.
            """
            #[...]

     -  Symbols can be used in equations:

        - |sum| |alpha|/\ *x* |le| |beta|

        |larr| and |larr| both give left
        arrows.  Some other arrows are
        |rarr|, |uarr|, and |darr|.

Although symbols can be quite useful, you should keep in mind that they can
make it harder to read your docstring in plaintext. In general, symbols should
be used sparingly. For a complete list of the symbols that are currently
supported, see the reference documentation for :epydoc:`epytext.SYMBOLS`.


Escaping
''''''''

Escaping is used to write text that would otherwise be interpreted as epytext
markup. Epytext was carefully constructed to minimize the need for this type
of escaping; but sometimes, it is unavoidable. Escaped text has the form
'``E{``\ *code*\ ``}``', where code is an escape code that specifies what
character should be produced. If the escape code is a single character (other
than '``{``' or '``}``'), then that character is produced. For example, to
begin a paragraph with a dash (which would normally signal a list item), write
'``E{-}``'. In addition, two special escape codes are defined: '``E{lb}``'
produces a left curly brace ('``{``'); and '``E{rb}``' produces a right curly
brace ('``}``'). The following example illustrates how escaping can be used:


.. list-table::
   :header-rows: 1

   * - Docstring Input
     - Rendered Output

   * - .. python::

        def example():
            """
            This paragraph ends with two
            colons, but does not introduce
            a literal blockE{:}E{:}

            E{-} This is not a list item.

            Escapes can be used to write
            unmatched curly braces:
            E{rb}E{lb}
            """
            #[...]

     -  This paragraph ends with two colons, but does not introduce a literal
        block:\ :

        \- This is not a list item.

        Escapes can be used to write unmatched curly braces: }{


Graphs
''''''

The inline markup construct '``G{``\ *graphtype args...*\ ``}``' is used to
insert automatically generated graphs. The following graphs generation
constructions are currently defines:

======================================= =======================================
Markup                                  Description
======================================= =======================================
``G{classtree``  *classes...*\ ``}``    Display a class hierarchy for the given
                                        class or classes (including all
                                        superclasses & subclasses). If no class
                                        is specified, and the directive is used
                                        in a class's docstring, then that
                                        class's class hierarchy will be
                                        displayed. 
``G{packagetree``  *modules...*\ ``}``  Display a package hierarchy for the
                                        given module or modules (including all
                                        subpackages and submodules). If no
                                        module is specified, and the directive
                                        is used in a module's docstring, then
                                        that module's package hierarchy will be
                                        displayed. 
``G{importgraph``  *modules...*\ ``}``  Display an import graph for the given
                                        module or modules. If no module is
                                        specified, and the directive is used in
                                        a module's docstring, then that
                                        module's import graph will be
                                        displayed.
``G{callgraph``  *functions...*\ ``}``  Display a call graph for the given
                                        function or functions. If no function
                                        is specified, and the directive is used
                                        in a function's docstring, then that
                                        function's call graph will be
                                        displayed.
======================================= =======================================


Characters
----------

Valid Characters
''''''''''''''''

Valid characters for an epytext docstring are space (``\040``); newline
(``\012``); and any letter, digit, or punctuation, as defined by the current
locale. Control characters (``\000``-``\010` and ``\013``-``\037``) are not
valid content characters. Tabs (``\011``) are expanded to spaces, using the
same algorithm used by the Python parser. Carridge-return/newline pairs
(``\015\012``) are converted to newlines.


Content Characters
''''''''''''''''''

Characters in a docstring that are not involved in markup are called *content characters*. Content characters are always displayed as-is. In particular, HTML
codes are not passed through. For example, consider the following example:

.. list-table::
   :header-rows: 1

   * - Docstring Input
     - Rendered Output

   * - .. python::

        def example():
            """
            <B>test</B>
            """
            #[...]

     -  <B>test</B>

The docstring is rendered as ``<B>test</B>``, and not as the word "test" in
bold face.


Spaces and Newlines
'''''''''''''''''''

In general, spaces and newlines within docstrings are treated as soft spaces.
In other words, sequences of spaces and newlines (that do not contain a blank
line) are rendered as a single space, and words may wrapped at spaces. However,
within literal blocks and doctest blocks, spaces and newlines are preserved,
and no word-wrapping occurs; and within URL targets and documentation link
targets, whitespace is ignored.
