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 done with Pygments (if it’s installed) 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:: 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:: ruby
  
     Some Ruby code.
  

  The directive’s alias name sourcecode works as well.

• The valid values for the highlighting language are:

  • none (no highlighting)
  • python (the default when highlight_language isn’t set)
  • guess (let Pygments guess the lexer based on contents, only works with certain well-recognizable languages)
  • rest
  • c
  • ... and any other lexer name that Pygments supports.

• If highlighting with the selected language fails, the block is not highlighted in any way.

Line numbers

If installed, 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
   :linenos:

   Some more Ruby code.

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.

Includes

.. 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 example.py, use:

.. literalinclude:: example.py

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.

The directive also supports the linenos flag option to switch on line numbers, 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
   :linenos:

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:: example.py
   :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:: example.py
   :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:: example.py
   :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.

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.

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.

Footnotes