What is Pylint?

From the FAQ:

Pylint is a static code checker, meaning it can analyse your code without actually running it.

Pylint checks for errors, tries to enforce a coding standard, and tries to enforce a coding style.

Resources

  • pylint.org
  • FAQ - in particular, see sections of message control and on working with other linters.

CLI

Help

$ pylint --help

Usage: pylint [options]

...

See also:

$ pylint --long-help

Flags

From the docs:

--ignore=<file[,file…]>
 	Add files or directories to the blacklist. They should be base names, not paths.
--output-format=<format>
 	Select output format (text, html, custom).
--msg-template=<template>
 	Modify text output message template.
--list-msgs	Generate pylint’s messages.
--full-documentation
 	Generate pylint’s full documentation, in reST format.

Example

Pass a file path.

$ pylint fizz.py
$ pylint fizz.py foo/bar.py

Pass a directory path.

$ pylint .
$ pylint foo

GUI

Requires tkinter.

$ pylint-gui

Generate config

The --generate-rcfile option will generate a commented configuration file on standard output according to the current configuration and exit.

$ pylint --generate-rcfile
$ pylint --generate-rcfile > .pylintrc

You might want to pass flags to it and see if those are saved.

Status codes

The exit codes of the pylint command:

Pylint returns bit-encoded exit codes. If applicable the table lists related stderr stream message output.

exit code meaning
0 no error
1 fatal message issued
2 error message issued
4 warning message issued
8 refactor message issued
16 convention message issued
32 usage error

Pylint exit package

Those are not so easy to read.

But you can use the pylint-exit library to give more useful messages printed and exit on a fatal error. You can also change the level by passing flags to it.

Here we run pylint-exit if pylint gave a non-zero status (which could be a warning error) and pass the pylint status code to pylint-exit.

$ pylint foo || pylint-exit $?

Config file

There are multiple names and places for a config, but the common choice is:

  • .pylintrc at the repo root.

Sample

Here ignoring FIXME comments, except Exception lines, and naming (such as when you do want a single-character variable name).

[MESSAGES CONTROL]
disable=
  fixme,
  broad-except,
  invalid-name

Also look at disabling global-statement to avoid error on use of global.

Generate

$ pylint --disable=bare-except,invalid-name --class-rgx='[A-Z][a-z]+' --generate-rcfile

You can generate a sample pylintrc file with --generate-rcfile.

Every option present on the command line before this will be included in the rc file

For example:

$ pylint --disable=bare-except,invalid-name --class-rgx='[A-Z][a-z]+' --generate-rcfile

Ignore

Disable rules for a scope.

The rules are comma-separated and you can also add a space after the comma.

Disable current line

# pylint: disable=RULES

e.g.

global VAR # pylint: disable=global-statement

# pylint: disable=fixme,line-too-long

Disable next line

# pylint: disable-next=...

Disable for a block

A block is either a scope (say a function, a module), or a multiline statement (try, finally, if statements, for loops).

It’s currently impossible to disable inside an else block

def my_function():
    # pylint: disable=some-rule

Disable for module

Place at the top of the file:

# pylint: disable=wildcard-import, method-hidden
# pylint: enable=too-many-lines

Or ignore the whole file:

# pylint: skip-file