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

Syntax highlighting is done with Pygments and 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, but the doc-wide default can be set with the highlight_language config value.

  • Within Python highlighting mode, interactive sessions are recognized automatically and highlighted appropriately. Normal Python code is only highlighted if it is parseable (so you can use Python as the default, but interspersed snippets of shell commands or other code blocks will not be highlighted as Python).

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

    .. highlight:: language


    .. highlight:: c

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

  • For documents that have to show snippets in different languages, there’s also a code-block directive that is given the highlighting language directly:

    .. code-block:: language

    Use it like this:

    .. code-block:: ruby
       Some Ruby code.

    The directive’s alias name sourcecode works as well.

  • The valid values for the highlighting language are:

  • If highlighting with the selected language fails (i.e. Pygments emits an “Error” token), the block is not highlighted in any way.

Line numbers

Pygments can generate line numbers for code blocks. For automatically-highlighted blocks (those started by ::), line numbers must be switched on in a highlight directive, with the linenothreshold option:

.. highlight:: python
   :linenothreshold: 5

This will produce line numbers for all code blocks longer than five lines.

For code-block blocks, a linenos flag option can be given to switch on line numbers for the individual block:

.. code-block:: ruby

   Some more Ruby code.

The first line number can be selected with the lineno-start option. If present, linenos is automatically activated as well.

Some more Ruby code, with line numbering starting at 10.

Additionally, an emphasize-lines option can be given to have Pygments emphasize particular lines:

.. code-block:: python
   :emphasize-lines: 3,5

   def some_function():
       interesting = False
       print 'This line is highlighted.'
       print 'This one is not...'
       print '...but this one is.'

Changed in version 1.1: emphasize-lines has been added.

Changed in version 1.3: lineno-start has been added.


.. literalinclude:: filename

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, use:

.. literalinclude::

The file name is usually relative to the current file’s path. However, if it is absolute (starting with /), it is relative to the top source directory.

Tabs in the input are expanded if you give a tab-width option with the desired tab width.

Like code-block, the directive supports the linenos flag option to switch on line numbers, the lineno-start option to select the first line number, the emphasize-lines option to emphasize particular lines, and a language option to select a language different from the current file’s standard language. Example with options:

.. literalinclude:: example.rb
   :language: ruby
   :emphasize-lines: 12,15-18

Include files are assumed to be encoded in the source_encoding. If the file has a different encoding, you can specify it with the encoding option:

.. literalinclude::
   :encoding: latin-1

The directive also supports including only parts of the file. If it is a Python module, you can select a class, function or method to include using the pyobject option:

.. literalinclude::
   :pyobject: Timer.start

This would only include the code lines belonging to the start() method in the Timer class within the file.

Alternately, you can specify exactly which lines to include by giving a lines option:

.. literalinclude::
   :lines: 1,3,5-10,20-

This includes the lines 1, 3, 5 to 10 and lines 20 to the last line.

Another way to control which part of the file is included is to use the start-after and end-before options (or only one of them). If start-after is given as a string option, only lines that follow the first line containing that string are included. If end-before is given as a string option, only lines that precede the first lines containing that string are included.

With lines selected using start-after it is still possible to use lines, the first allowed line having by convention the line number 1.

When lines have been selected in any of the ways described above, the line numbers in emphasize-lines also refer to the selection, with the first selected line having number 1.

When specifying particular parts of a file to display, it can be useful to display the original line numbers. This can be done using the lineno-match option, which is however allowed only when the selection consists of contiguous lines.

You can prepend and/or append a line to the included code, using the prepend and append option, respectively. This is useful e.g. for highlighting PHP code that doesn’t include the <?php/?> markers.

If you want to show the diff of the code, you can specify the old file by giving a diff option:

.. literalinclude::

This shows the diff between and with unified diff format.

New in version 0.4.3: The encoding option.

New in version 0.6: The pyobject, lines, start-after and end-before options, as well as support for absolute filenames.

New in version 1.0: The prepend and append options, as well as tab-width.

New in version 1.3: The diff option. The lineno-match option.

Changed in version 1.6: With both start-after and lines in use, the first line as per start-after is considered to be with line number 1 for lines.

Caption and name

New in version 1.3.

A caption option can be given to show that name before the code block. A name option can be provided implicit target name that can be referenced by using ref. For example:

.. code-block:: python
   :name: this-py

   print 'Explicit is better than implicit.'

literalinclude also supports the caption and name option. caption has an additional feature that if you leave the value empty, the shown filename will be exactly the one given as an argument.


New in version 1.3.

A dedent option can be given to strip indentation characters from the code block. For example:

.. literalinclude:: example.rb
   :language: ruby
   :dedent: 4
   :lines: 10-15

code-block also supports the dedent option.


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