How To Write a Pylint Plugin

Pylint provides support for writing two types of extensions. First, there is the concept of checkers, which can be used for finding problems in your code. Secondly, there is also the concept of transform plugin, which represents a way through which the inference and the capabilities of Pylint can be enhanced and tailored to a particular module, library of framework.

In general, a plugin is a module which should have a function register, which takes an instance of pylint.lint.PyLinter as input.

A plugin can optionally define a function, load_configuration, which takes an instance of pylint.lint.PyLinter as input. This function is called after Pylint loads configuration from configuration file and command line interface. This function should load additional plugin specific configuration to Pylint.

So a basic hello-world plugin can be implemented as:

# Inside hello_plugin.py
from typing import TYPE_CHECKING

import astroid

if TYPE_CHECKING:
    from pylint.lint import PyLinter


def register(linter: "PyLinter") -> None:
  """This required method auto registers the checker during initialization.

  :param linter: The linter to register the checker to.
  """
  print('Hello world')

We can run this plugin by placing this module in the PYTHONPATH and invoking pylint as:

$ pylint -E --load-plugins hello_plugin foo.py
Hello world

We can extend hello-world plugin to ignore some specific names using load_configuration function:

# Inside hello_plugin.py
from typing import TYPE_CHECKING

import astroid

if TYPE_CHECKING:
    from pylint.lint import PyLinter


def register(linter: "PyLinter") -> None:
  """This required method auto registers the checker during initialization.

  :param linter: The linter to register the checker to.
  """
  print('Hello world')

def load_configuration(linter):

  name_checker = get_checker(linter, NameChecker)
  # We consider as good names of variables Hello and World
  name_checker.config.good_names += ('Hello', 'World')

  # We ignore bin directory
  linter.config.black_list += ('bin',)

Depending if we need a transform plugin or a checker, this might not be enough. For the former, this is enough to declare the module as a plugin, but in the case of the latter, we need to register our checker with the linter object, by calling the following inside the register function:

linter.register_checker(OurChecker(linter))

For more information on writing a checker see How to Write a Checker.