Frequently Asked Questions#

How do I install Pylint?#

Everything should be explained on Command line installation.

What kind of versioning system does Pylint use?#

Pylint uses git. To get the latest version of Pylint from the repository, simply invoke

git clone https://github.com/PyCQA/pylint

3. Running Pylint#

3.1 Where is the persistent data stored to compare between successive runs?#

Analysis data are stored as a pickle file in a directory which is localized using the following rules:

  • value of the PYLINTHOME environment variable if set

  • "pylint" subdirectory of the user's XDG_CACHE_HOME if the environment variable is set, otherwise

    • Linux: "~/.cache/pylint"

    • Mac OS X: "~/Library/Caches/pylint"

    • Windows: "C:Users<username>AppDataLocalpylint"

  • ".pylint.d" directory in the current directory

3.2 How do I find the option name corresponding to a specific command line option?#

You can generate a sample configuration file with --generate-toml-config. Every option present on the command line before this will be included in the toml file

For example:

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

4. Message Control#

4.1 How to disable a particular message?#

For just a single line, add #pylint: disable=some-message,another-one at the end of the desired line of code. Since Pylint 2.10 you can also use #pylint: disable-next=... on the line just above the problem. ... in the following example is short for the list of messages you want to disable.

For larger amounts of code, you can add #pylint: disable=... at the block level to disable messages for the entire block. It's possible to re-enable a message for the remainder of the block with #pylint: enable=.... A block is either a scope (say a function, a module) or a multiline statement (try, finally, if statements, for loops). Note: It's currently impossible to disable inside an else block.

Read Messages control for details and examples.

4.2 Is there a way to disable a message for a particular module only?#

Yes, you can disable or enable (globally disabled) messages at the module level by adding the corresponding option in a comment at the top of the file:

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

4.3 How can I tell Pylint to never check a given module?#

Add #pylint: skip-file at the beginning of the module.

In order to ease finding which modules are ignored an Information-level message file-ignored is emitted.

4.4 Do I have to remember all these numbers?#

No, you can use symbolic names for messages:

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

4.5 I have a callback function where I have no control over received arguments. How do I avoid getting unused argument warnings?#

Prefix (ui) the callback's name by cb_, as in cb_onclick(...). By doing so arguments usage won't be checked. Another solution is to use one of the names defined in the "dummy-variables" configuration variable for unused argument ("_" and "dummy" by default).

4.6 What is the format of the configuration file?#

Pylint uses ConfigParser from the standard library to parse the configuration file. It means that if you need to disable a lot of messages, you can use any formatting accepted by ConfigParser, e.g.

[MAIN]
output-format = colorized

[Messages Control]
disable=method-hidden,too-many-lines,wildcard-import
[Messages Control]
disable =
    method-hidden
    too-many-lines
    wildcard-import

Alternatively, if you use pyproject.toml, e.g.

[tool.pylint.main]
output-format = "colorized"

[tool.pylint.messages_control]
disable = [
    "method-hidden",
    "too-many-lines",
    "wildcard-import",
]

See also the exhaustive list of possible options.

4.7 Why are there a bunch of messages disabled by default?#

pylint does have some messages disabled by default, either because they are prone to false positives or that they are opinionated enough for not being included as default messages.

You can see the plugin you need to explicitly load in the technical reference.

5.1 When is Pylint considering a class as an abstract class?#

A class is considered as an abstract class if at least one of its methods is doing nothing but raising NotImplementedError.

5.2 How do I avoid "access to undefined member" messages in my mixin classes?#

You should add the no-member message to your ignored-checks-for-mixins option and name your mixin class with a name which ends with "Mixin" or "mixin" (default) or change the default value by changing the mixin-class-rgx option.

6. Troubleshooting#

6.1 Pylint gave my code a negative rating out of ten. That can't be right!#

Prior to Pylint 2.13.0, the score formula used by default had no lower bound. The new default score formula is

max(0, 0 if fatal else 10.0 - ((float(5 * error + warning + refactor + convention) / statement) * 10))

If your project contains a configuration file created by an earlier version of Pylint, you can set evaluation to the above expression to get the new behavior. Likewise, since negative values are still technically supported, evaluation can be set to a version of the above expression that does not enforce a floor of zero.