Documenting class-level variables in Python

Question

I am trying to document a Python class that has some class-level member variables, but I could not get it appropriately documented using reST/Sphinx.

The code is this:

class OSM:
    """Some blah and examples"""
    url = 'http://overpass-api.de/api/interpreter'  # URL of the Overpass API
    sleep_time = 10  # pause between successive queries when assembling OSM dataset

But I get this output (see the green circled area, where I would like to have some text describing both variables, as above).

I apologize for the blurring, but part of the example is somewhat sensitive

Answer 1

You have several options to document class level variables.

1. Put a comment that starts with #: before the variable, or on the same line. (Uses only autodoc.)

   Perhaps the easiest choice. If needed you can customize the value using :annotation: option. If you want to type-hint the value use #: type:.

2. Put a docstring after the variable.

   Useful if the variable requires extensive documentation.

   For module data members and class attributes, documentation can either be put into a comment with special formatting (using a #: to start the comment instead of just #), or in a docstring after the definition. Comments need to be either on a line of their own before the definition, or immediately after the assignment on the same line. The latter form is restricted to one line only.

3. Document the variable in the class docstring. (Uses sphinx-napoleon extension, shown in the example.)

   This has the drawback that the variable's value will be omitted. Since it's a class level variable your IDE's static type checker may complain if you don't prefix the variable with cls. or class_name.. The distinction is however convenient because instance variables can also be documented in the class docstring.

The following example shows all three options. The .rst has additional complexity to illustrate the neededautodoc functionalities. Type hints were included in all cases but can also be omitted.

class OSM:
    """Some blah and examples"""

    #: str: URL of the Overpass API.
    url = 'http://overpass-api.de/api/interpreter'
    #: int: pause between successive queries when assembling OSM dataset.
    sleep_time = 10


class OSM2:
    """Some blah and examples.

    Attributes:
        cls.url (str): URL of the Overpass API.
    """

    url = 'http://overpass-api.de/api/interpreter'

    sleep_time = 10
    """str: Docstring of sleep_time after the variable."""

Corresponding .rst

OSM module
==========

.. automodule:: OSM_module
    :members:
    :exclude-members: OSM2

    .. autoclass:: OSM2
        :no-undoc-members:
        :exclude-members: sleep_time

        .. autoattribute:: sleep_time
            :annotation: = "If you want to specify a different value from the source code."

The result:

Answer 2

This also works, if you're ok with suppressing a silly linter rule.

class OSM2:
    sleep_time = 10;  """str: Inline docstring of sleep_time after the variable."""