What's New in Pylint 4.1¶

:Release:4.1 :Date: TBA

Summary -- Release highlights¶

The required astroid version is now 4.1.1. See the astroid changelog for additional fixes, features, and performance improvements applicable to pylint.

What's new in Pylint 4.0.0-dev0?¶

Release date: TBA

New Features¶

Add support for ignore-pattern-in-long-lines to allow ignoring specific parts of a line when checking line length.

Refs #3352 (#3352)
The dict-init-mutate message now includes a suggested dictionary literal showing how to combine the initialization and subsequent mutations into a single statement.

Closes #7819 (#7819)
pyreverse: add --no-signatures to show method names without parameter lists or return type annotations in class diagrams.

Closes #10772 (#10772)
Add support for --known-first-party similar to --known-third-party.

Refs #10803 (#10803)

False Positives Fixed¶

Fix a false positive for too-many-arguments in (non-static) methods and classmethods.

Closes #8675 (#8675)
Fix used-before-assignment false positive for names bound in only some arms of an if/elif/else chain.

Closes #9879 (#9879)
Fix a false positive for unexpected-keyword-arg for dataclasses using generic type aliases (PEP 695).

Closes #10703 (#10703)
Fix possibly-used-before-assignment false positive when using self.fail() in tests.

Closes #10743 (#10743)
Fixed false positive for logging-unsupported-format when no arguments are provided to logging functions.

According to Python's logging documentation, no formatting is performed when no arguments are supplied, so strings like logging.error("%test") are valid.

Closes #10752 (#10752)
Fix false positive unreachable when calling a function with @overload where one signature returns NoReturn.

Closes #10785 (#10785)
Fix a false positive for too-many-function-args for dataclasses using generic type aliases (PEP 695).

Closes #10788 (#10788)
Fix a false positive for invalid-name where a dataclass field typed with Final was evaluated against the class_const regex instead of the class_attribute regex.

Closes #10790 (#10790)
Avoid emitting unspecified-encoding (W1514) when py-version is 3.15+.

Refs #10791 (#10791)
Fix a false positive relative-beyond-top-level error when linting specific files in namespace packages in parallel mode by augmenting sys.path before loading plugins and expanding files consistently for parallel workers.

Closes #10794 (#10794)
Fix undefined-variable false positive when a name used as a metaclass argument in a nested class is referenced again later in the module.

Closes #10823 (#10823)
Fix a false positive for unused-variable where global variables matching dummy-variables-rgx were still reported as unused when allow-global-unused-variables was disabled.

Closes #10890 (#10890)

Fix # pylint: enable inside a try block leaking into the except handler. For example in the following code, no-member is no longer incorrectly re-enabled in the except block:

class Basket:
    # pylint: disable=no-member
    def pick(self):
        try:
            # pylint: enable=no-member
            print(self.apple)  # no-member emitted here
        except KeyError:
            print(self.banana)  # no-member NOT emitted here (correct)

Requires astroid 4.2.

Refs #10933 (#10933)

Fix a false positive for bad-dunder-name when there is a user-defined __suppress_context__ attribute on exception subclasses.

Closes #10960 (#10960)
Fix used-before-assignment false positive for names bound by from X import * in every branch of an if/elif/else chain.

Refs #10980 (#10980)

Other Bug Fixes¶

Fix enabling checks from extensions which are disabled by default if multiple jobs are used.

Closes #10037 (#10037)
wrong-import-position now exempts try, if, with, and match blocks from marking the import boundary. Fixed async def not being detected as an import boundary. Pragma on non-import lines now suppresses following imports until the next non-import.

Closes #10589 (#10589)
Fix duplicate messages for extension checks if multiple jobs are used.

Refs #10642 (#10642)
Fix --known_third_party config being ignored.

Closes #10801 (#10801)
Fixed dynamic color mapping for "fail-on" messages when using multiple reporter/output formats.

Closes #10825 (#10825)
dependency on isort is now set to <9, permitting to use isort 8.

Closes #10857 (#10857)
Fix crash when checking attribute-defined-outside-init on classes that inherit from a base class pylint cannot fully analyze.

Closes #10892 (#10892)
Fixed inflated message occurrence counts in the final Messages report when running pylint in parallel mode with --jobs greater than 1.

Closes #10996 (#10996)

Other Changes¶

You can now set the files option in configuration files and on the command line. Passing files without the --files flag is still supported. This allows to set files to files = my_source_directory and invoking pylint with only the pylint command similar to how other CLI tools allow to do so. The help message can always be invoked with pylint -h or pylint --help.

Closes #5701 (#5701)
Document that the wrong-import-order (C0411) classification of imports as third-party vs first-party depends on the current working directory and recommend known-first-party as the deterministic workaround.

Closes #8801 (#8801)

Performance Improvements¶

Lazily import isort, dill, multiprocessing/concurrent.futures, and tomlkit so they are only loaded when actually needed. This reduces startup time by ~25% (e.g. --version: 91 => 67 ms, --help: 176 => 133 ms, single-file lint: 272 => 226 ms).

Closes #2866 (#2866)
The duplicate-code checker no longer runs when its message (R0801) is disabled, even if reports=yes is set. Previously, the checker's report (RP0801) would cause the expensive similarity computation to run regardless.

Closes #3443 (#3443)
Skip isort classification in the import checker when no import-ordering message is enabled, and cache the isort configuration so it is built once instead of once per import statement. Skipping the isort processing become a negligible improvement once the caching is applied. pylint became ~17% faster on ansible (~=4500 imports) even with isort enabled.

Refs #10886, #2866, #10637 (#10886)