SunPy Documentation Rules


All code must be documented and we follow these style conventions described here:

We recommend familiarizing yourself with these references.


The current differences we have are as follows:

We backtick each type in the documentation strings so that they are interlinked by our documentation builder:

x : `type`
   Description of parameter x.

SunPy Specific Rules

  • For all RST files, we enforce a one sentence per line rule and ignore the line length.

  • Core datatypes are referenced as follows:

smap : ``
    A SunPy map.
  • The Factory classes (Map, Timeseries, Fido) are referenced as follows:

`Map <>`
`Fido <>`
`TimeSeries <sunpy.timeseries.timeseries_factory.TimeSeriesFactory>`
  • Standards on docstring length and style are enforced using docformatter:

$ docformatter -r -i  --pre-summary-newline --make-summary-multi-line

Documenting Data Sources

Subclasses of GenericMap or TimeSeries must provide a detailed docstring providing an overview of the data source that the object represents. In order to maintain consistency and completeness, the following information must be provided by a data source docstring, if available, and preferably in the following order:

  • the name of the mission and instrument and the institution that built it

  • short description of the instrument (e.g. Cassegrain reflector, Wolter-1 grazing incidence x-ray, coronagraph) including the type of detector

  • description of the platform (e.g. satellite in 28 deg inclined orbit, a telescope on the summit of Mauna Kea in Hawaii)

  • description of the primary purpose or science goals of the instrument.

  • list of all wavelength(s) or passbands in appropriate units

  • description of the emission processes which dominate in those passbands

  • appropriate measurement properties such as field of view, angular resolution, time resolution

  • description of the operational concept (e.g. operates 24/7, observes from 7 am to 5 pm UT) including mention of unusual operations scenarios (e.g. calibration seasons, eclipse seasons)

  • the start and end of the data set

In addition, a reference section must be provided with links to the following resources, if available,

  • the mission web page

  • the instrument web page

  • relevant wikipedia page(s)

  • relevant user guide(s)

  • the mission paper and instrument paper

  • information to interpret metadata keywords such as FITS header reference

  • the data archive

An example docstring can be found in the Writing a new Instrument Map Class guide.


All of the SunPy documentation (like this page) is built by Sphinx, which is a tool especially well-suited for documenting Python projects. Sphinx works by parsing files written using a a Mediawiki-like syntax called reStructuredText. In addition to parsing static files of reStructuredText, Sphinx can also be told to parse code comments. In fact, in addition to what you are reading right now, the Python documentation was also created using Sphinx.


All of the SunPy documentation is contained in the “docs” folder and code docstings/comments. The examples from the example gallery can be found in the “examples” folder. To build the documentation locally you must have all the dependencies (pip install -e .[docs]) specified in setup.cfg installed on your computer.

In the root directory run:

$ tox -e build_docs

This will generate HTML documentation for SunPy in the “docs/_build/html” directory. You can open the “index.html” file to browse the final product. The gallery examples are located under “docs/_build/html/generated/gallery”. Sphinx builds documentation iteratively, only adding things that have changed. If you’d like to start from scratch then just run:

$ tox -e build_docs -- -aE

For more information on how to use Sphinx, consult the Sphinx documentation.


Sphinx can be very particular about formatting, and the warnings and errors aren’t always obvious.

Below are some commonly-encountered warning/error messages along with a human-readable translation:

WARNING: Duplicate explicit target name: “xxx”.

If you reference the same URL, etc more than once in the same document sphinx will complain. To avoid, use double-underscores instead of single ones after the URL.

ERROR: Malformed table. Column span alignment problem at line offset n

Make sure there is a space before and after each colon in your class and function docs (e.g. attribute : type, instead of attribute: type). Also, for some sections (e.g. Attributes) numpydoc seems to complain when a description spans more than one line, particularly if it is the first attribute listed.

WARNING: Block quote ends without a blank line; unexpected unindent.

Lists should be indented one level from their parents.

ERROR: Unknown target name: “xxx”

In addition to legitimate errors of this type, this error will also occur when variables have a trailing underscore, e.g., xxx_.

WARNING: Explicit markup ends without a blank line; unexpected unindent.

This usually occurs when the text following a directive is wrapped to the next line without properly indenting a multi-line text block.

WARNING: toctree references unknown document ‘…’ / WARNING: toctree contains reference to nonexisting document

This pair of errors is due to the way numpydoc scrapes class members.