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pydoclint

A Python docstring linter to check whether a docstring's sections (arguments, returns, raises, ...) match the function signature or function implementation.

It runs really fast. In fact, it is at least ~1,475 times faster than darglint (another linter of the same purposes which is no longer maintained).

Here is a comparison of linting time on some famous Python projects:

pydoclint darglint
numpy 2.0 sec 49 min 9 sec (1,475x slower)
scikit-learn 2.4 sec 3 hr 5 min 33 sec (4,639x slower)

Currently, pydoclint supports two docstring styles:

Support for the Sphinx style may be added in the future if there are requests for it.

Another note: this linter and pydocstyle serves complementary purposes. It is recommended that you use both together.

1. Installation

pip install pydoclint

Note that pydoclint currently only supports Python 3.8 and above. (Python 3.7 support may be added if there are interests and requests.)

2. Usage

2.1. As a native command line tool

pydoclint <FILE_OR_FOLDER>

Replace <FILE_OR_FOLDER> with the file/folder names you want, such as ..

2.2. As a flake8 plugin

Once you install pydoclint you will have also installed flake8. Then you can run:

flake8 --select=DOC <FILE_OR_FOLDER>

If you don't include --select=DOC in your command, flake8 will also run other built-in flake8 linters on your code.

2.3. Native vs flake8

Should I use pydoclint as a native command line tool or a flake8 plugin? Here's comparison:

Pros Cons
Native tool Slightly faster No inline or project-wide omission support right now [*]
flake8 plugin Supports inline or project-wide omission Slightly slower because other flake8 plugins are run together

*) This feature may be added in the near future

2.4. Configuration

Here is how to configure pydoclint. For detailed explanations of all options, see Section 4 below.

2.4.1. Setting options inline

  • Native:

    pydoclint --check-arg-order=False <FILE_OR_FOLDER_PATH>

  • Flake8:

    flake8 --check-arg-order=False <FILE_OR_FOLDER_PATH>

2.4.2. Setting options in a configuration file

  • Native:

    • In a .toml file somewhere in your project folder, add a section like this (put in the config that you need):

      [tool.pydoclint]
style = 'google'
exclude = '\.git|\.tox|tests/data|some_script\.py'
require-return-section-when-returning-none = true

    • Then, specify the path of the .toml file in your command:

      pydoclint --config=path/to/my/config.toml <FILE_OR_FOLDER_PATH>

  • Flake8:

    • In your flake8 config file (see flake8's official doc), add the config you need under the section [flake8]

3. Style violation codes

pydoclint currently has the following style violation codes:

3.0. DOC0xx: Docstring parsing issues

Code Explanation
DOC001 Potential formatting errors in docstring

3.1. DOC1xx: Violations about input arguments

Code Explanation
DOC101 Docstring contains fewer arguments than in function signature
DOC102 Docstring contains more arguments than in function signature
DOC103 Docstring arguments are different from function arguments. (Or could be other formatting issues: https://github.com/jsh9/pydoclint#notes-on-doc103)
DOC104 Arguments are the same in the docstring and the function signature, but are in a different order.
DOC105 Argument names match, but type hints do not match

Notes on DOC103:

Other potential causes to DOC103 include:

  • Numpy docstring style requires this style: arg1 : int (a space between arg1 and :) but people sometimes write arg1: int. This will trigger DOC103.
  • In the Google style, writing an Args: section without the preceding summary will also trigger DOC103.

3.2. DOC2xx: Violations about return argument(s)

Code Explanation
DOC201 Function/method does not have a return section in docstring
DOC202 Function/method has a return section in docstring, but there are no return statements or annotations

Note on DOC201: Methods with @property as its last decorator do not need to have a return section.

3.3. DOC3xx: Violations about class docstring and class constructor

Code Explanation
DOC301 __init__() should not have a docstring; please combine it with the docstring of the class
DOC302 The class docstring does not need a "Returns" section, because __init__() cannot return anything
DOC303 The __init__() docstring does not need a "Returns" section, because it cannot return anything
DOC304 Class docstring has an argument/parameter section; please put it in the __init__() docstring
DOC305 Class docstring has a "Raises" section; please put it in the __init__() docstring
DOC306 The class docstring does not need a "Yields" section, because __init__() cannot yield anything
DOC307 The __init__() docstring does not need a "Yields" section, because __init__() cannot yield anything

3.4. DOC4xx: Violations about "yield" statements

Code Explanation
DOC401 Function/method returns a Generator, but the docstring does not have a "Yields" section
DOC402 Function/method has "yield" statements, but the docstring does not have a "Yields" section
DOC403 Function/method has a "Yields" section in the docstring, but there are no "yield" statements or a Generator return annotation

3.5. DOC5xx: Violations about "raise" statements

Code Explanation
DOC501 Function/method has "raise" statements, but the docstring does not have a "Raises" section
DOC502 Function/method has a "Raises" section in the docstring, but there are not "raise" statements in the body

4. Configuration options

There are several configuration options available. They can be used invidually or together.

4.1. --quiet (shortform: -q)

This flag activates the "quite mode", in which no output will be printed to the command line if there are no violations.

By default, this flag is not activated, so the files that are scanned are printed in the command line.

pydoclint --quiet <FILE_OR_FOLDER>

This option is only available in the "native" command-line mode, rather than in flake8. If you use pydoclint in flake8, please use flake8's own verbosity configuration instead.

4.2. --exclude

You can use this option to exclude files within the given folder. It is a regex pattern of full file paths.

For example:

pydoclint --exclude='\.git|\.tox|tests/data' <FOLDER_NAME>

This option is only available in the native command-line mode. If you use pydoclint within flake8, you can use flake8's --exclude option.

4.3. --style

Which style of docstring is your code base using. Right now there are two available choices: numpy and google. The default value is numpy.

pydoclint --style=google <FILE_OR_FOLDER>

or

flake8 --style=google <FILE_OR_FOLDER>

4.4. --check-type-hint (shortform: -th, default: True)

If True, the type hints in the docstring and in the Python code need to exactly match.

To turn this option on/off, do this:

pydoclint --check-type-hint=False <FILE_OR_FOLDER>

or

flake8 --check-type-hint=False <FILE_OR_FOLDER>

4.5. --check-arg-order (shortform: -ao, default: True)

If True, the input argument order in the docstring needs to match that in the function signature.

To turn this option on/off, do this:

pydoclint --check-arg-order=False <FILE_OR_FOLDER>

or

flake8 --check-arg-order=False <FILE_OR_FOLDER>

4.6. --skip-checking-short-docstrings (shortform: -scsd, default: True)

If True, pydoclint won't check functions that have only a short description in their docstring.

To turn this option on/off, do this:

pydoclint --skip-checking-short-docstrings=False <FILE_OR_FOLDER>

or

flake8 --skip-checking-short-docstrings=False <FILE_OR_FOLDER>

4.7. --skip-checking-raises (shortform: -scr, default: False)

If True, pydoclint won't report DOC501 or DOC502 if there are raise statements in the function/method but there aren't any "raises" sections in the docstring (or vice versa).

4.8. --allow-init-docstring (shortform: -aid, default: False)

If it is set to True, having a docstring for class constructors (__init__()) is allowed, and the arguments are expected to be documented under __init__() rather than in the class docstring.

4.9. --require-return-section-when-returning-none (shortform: -rrs, default: False)

If False, a "return" section is not necessary in the docstring if the function implicitly returns None (for example, doesn't have a return statement, or has -> None as the return annotation).