Documentation


Professor Carole Goble in “Better Software, Better Research”:

One of my favorite #overlyhonestmethods tweets (a hashtag for lab scientists) is Ian Holmes’s “You can download our code from the URL supplied. Good luck downloading the only postdoc who can get it to run, though.

Value of documentation


  • The value and extent of your work is clearer if it can be understood by colleagues.
  • Documentation provides provenance for your scientific process, for your colleagues and yourself.
  • Documentation demonstrates your skill and professionalism.

Documentation is easier than you think.


  • Documentation pays for itself with the time it saves in the long run.
  • Documentation requires little effort beyond writing the software itself.

Types of documentation


  • Theory manuals
  • User and developer guides
  • Code comments
  • Self-documenting code
  • Generated API documentation

User and developer guides


README: sits in top-level directory and contains all the necessary information for installing, getting started with, and understanding the accompanying code.

May be accompanied by other specific files: LICENSE, INSTALL, CITATION, ABOUT, CHANGELOG

README example



                            SQUIRREL, version 1.2 released on 2026-09-20

                            # About

                            The Spectral Q and U Imaging Radiation Replicating Experimental Library
                            (SQUIRREL) is a library for replicating radiation sources with spectral details
                            and Q and U polarizations of superman bubblegum.

                            # Installation

                            The SQUIRREL library relies on other libraries:

                            - The ACORN library www.acorn.nutz
                            - The TREEBRANCH database format API

                            Install those before installing the SQUIRREL library. To install the SQUIRREL
                            library:

                            ./configure
                            make --prefix=/install/path
                            make install
                            ...
                        

Comments


Comments provide a way to insert metainformation about code intended for people, right next to the code:


                            def the_function(var):
                                """This is a docstring, where a function 
                                definition might live"""
                                a = 1 + var # this is a simple comment
                                return a
                        

Bad Comments


Also possible to pollute code with unnecessary cruft:


                            def decay(index, database):
                                # first, retrieve the decay constants from the database
                                mylist = database.decay_constants()
                                # next, try to access an element of the list
                                try:
                                    # gets decay constant at index in the list
                                    d = mylist[index]
                                # if the index doesn't exist
                                except IndexError:
                                    # throw an informative error message
                                    raise Exception("value not found in the list")
                                return d
                        

Useful Comments

Code written cleanly will have its own voice. Use intelligent naming to make most lines of code clear without comments, then use comments sparingly to help explain reasons or complicated sections:


                            def decay(index, database):
                                lambdas = database.decay_constants()
                                try:
                                    # gets decay constant at index in the list
                                    lambda_i = lambdas[index]
                                except IndexError:
                                    raise Exception("value not found in the list")
                                return lambda
                        

Self-Documenting Code


Naming: a class, variable, or function name should tell you why it exists, what it does, and how it is used.

Simple functions: functions should be small to be understandable and testable; they should only do one thing.

Consistent style: use a consistent, standardized style; e.g., select variable and function names according to the PEP8 style guide for Python.

Guidelines for naming:


                            ## packages and modules are short and lowercase
                            packages
                            modules

                            ## other objects can be long
                            ClassesUseCamelCase
                            ExceptionsAreClassesToo
                            functions_use_snake_case
                            CONSTANTS_USE_ALL_CAPS

                            ## variable scope is *suggested* by style convention
                            # internal to module
                            _single_leading_underscore_
                            # avoids conflicts with Python keywords
                            single_trailing_underscore_
                            # these are magic, like __init__
                            __double_leading_and_trailing__
                        

Examples of helpful naming:


All should be human-readable phrases

Functions/methods: these are actions and should be verbs

Booleans: "is_something"

Most important: be consistent!

Docstrings


docstring: comment placed immediately after a function or class definition, typically enclosed by three pairs of double quotes:


                            def <name>(<args>):
                                """<docstring>"""
                                <body>
                        

docstrings are available within Python via help() and iPython's magic command ?, and Sphinx picks them up.

Docstrings (more)


Make docstrings descriptive and concise; you can explain the arguments of a function, its behavior, and how you intend it to be used.


                            def power(base, x):
                                """Computes base^x. Both base and x should be integers,
                                floats, or another numeric type.
                                """
                                return base**x
                        

Sphinx: automate generating documentation


Sphinx can be used to automate the generation of HTML documentation; we can even use it with Travis CI to automatically build and deploy the docs on GitHub Pages.

For now, let's just make sure your docstrings are suitable for Sphinx.

Numpy-Style Docstrings



                            def function_with_types_in_docstring(param1, param2):
                                """Example function with types documented in the docstring.

                                `PEP 484`_ type annotations are supported. If attribute, parameter, and
                                return types are annotated according to `PEP 484`_, they do not need to be
                                included in the docstring:

                                Parameters
                                ----------
                                param1 : int
                                    The first parameter.
                                param2 : str
                                    The second parameter.

                                Returns
                                -------
                                bool
                                    True if successful, False otherwise.

                                .. _PEP 484:
                                    https://www.python.org/dev/peps/pep-0484/

                                """
                        

More examples at the Sphinx documentation

Google-Style Docstrings



                            def function_with_types_in_docstring(param1, param2):
                                """Example function with types documented in the docstring.

                                `PEP 484`_ type annotations are supported. If attribute, parameter, and
                                return types are annotated according to `PEP 484`_, they do not need to be
                                included in the docstring:

                                Args:
                                    param1 (int): The first parameter.
                                    param2 (str): The second parameter.

                                Returns:
                                    bool: The return value. True for success, False otherwise.

                                .. _PEP 484:
                                    https://www.python.org/dev/peps/pep-0484/

                                """
                        

More examples at the Sphinx documentation

Contents of sphinx.yml:


                            name: "Sphinx: Render docs"

                            on: push
                            
                            jobs:
                              build:
                                runs-on: ubuntu-latest
                                permissions:
                                  contents: write
                                steps:
                                - uses: actions/checkout@v4
                                - name: Set up Python
                                  uses: actions/setup-python@v2
                                  with:
                                    python-version: '3.12'
                                - name: Install dependencies
                                  run: |
                                    python3 -m pip install --upgrade pip
                                    pip install . sphinx myst_parser
                                - name: Build HTML
                                  run: |
                                    cd docs
                                    make html
                                - name: Upload artifacts
                                  uses: actions/upload-artifact@v4
                                  with:
                                    name: html-docs
                                    path: docs/build/html/
                                - name: Deploy
                                  uses: peaceiris/actions-gh-pages@v3
                                  if: github.ref == 'refs/heads/main'
                                  with:
                                    github_token: ${{ secrets.GITHUB_TOKEN }}
                                    publish_dir: docs/build/html
                          

Semantic Versioning: Given a version number MAJOR.MINOR.PATCH, increment the:

  • MAJOR version when you make incompatible API changes,
  • MINOR version when you add functionality in a backwards-compatible manner, and
  • PATCH version when you make backwards-compatible bug fixes.

To start: set initial development release at 0.1.0 and increment minor version for subsequent releases.

Contents of _version.py:



                            __version_info__ = (0, 4, 2, 'a1')
                            __version__ = '.'.join(map(str, __version_info__[:3]))
                            if len(__version_info__) == 4:
                                __version__ += __version_info__[-1]
                        

Then in pyproject.toml:



                            [project]
                            dynamic = ["version"]

                            [tool.hatch]
                            version.path = "src/[package]/_version.py"