Summary -- Release highlights

New checkers

  • A new check isinstance-second-argument-not-valid-type was added.

    This check is emitted whenever pylint finds a call to the isinstance function with a second argument that is not a type. Such code is likely unintended as it will cause a TypeError to be thrown at runtime error.

  • A new check assert-on-string-literal was added.

    This check is emitted whenever pylint finds an assert statement with a string literal as its first argument. Such assert statements are probably unintended as they will always pass.

  • A new check f-string-without-interpolation was added.

    This check is emitted whenever pylint detects the use of an f-string without having any interpolated values in it, which means that the f-string can be a normal string.

  • Multiple checks for invalid return types of protocol functions were added:

    • invalid-bool-returned: __bool__ did not return a bool

    • invalid-index-returned: __index__ did not return an integer

    • invalid-repr-returned): __repr__ did not return a string

    • invalid-str-returned): __str__ did not return a string

    • invalid-bytes-returned): __bytes__ did not return a string

    • invalid-hash-returned): __hash__ did not return an integer

    • invalid-length-hint-returned): __length_hint__ did not return a non-negative integer

    • invalid-format-returned): __format__ did not return a string

    • invalid-getnewargs-returned): __getnewargs__ did not return a tuple

    • invalid-getnewargs-ex-returned): __getnewargs_ex__ did not return a tuple of the form (tuple, dict)

  • A new check inconsistent-quotes was added.

    This check is emitted when quotes delimiters (" and ') are not used consistently throughout a module. It allows avoiding unnecessary escaping, allowing, for example, "Don't error" in a module in which single-quotes otherwise delimit strings so that the single quote in Don't doesn't need to be escaped.

  • A new check non-str-assignment-to-dunder-name was added to ensure that only strings are assigned to __name__ attributes.

Other Changes

  • Configuration can be read from a setup.cfg or pyproject.toml file in the current directory. A setup.cfg must prepend pylintrc section names with pylint., for example [pylint.MESSAGES CONTROL]. A pyproject.toml file must prepend section names with tool.pylint., for example [tool.pylint.'MESSAGES CONTROL']. These files can also be passed in on the command line.

  • Add new good-names-rgx and bad-names-rgx to enable permitting or disallowing of names via regular expressions

    To enable better handling of permitted/disallowed names, we added two new config options: good-names-rgxs: a comma- separated list of regexes, that if a name matches will be exempt of naming-checking. bad-names-rgxs: a comma- separated list of regexes, that if a name matches will be always marked as a disallowed name.

  • Mutable collections.* are now flagged as dangerous defaults.

  • Add new --fail-under flag for setting the threshold for the score to fail overall tests. If the score is over the fail-under threshold, pylint will complete SystemExit with value 0 to indicate no errors.

  • Added a new option notes-rgx to make fixme warnings more flexible. Now either notes or notes-rgx option can be used to detect fixme warnings.

  • Non-ASCII characters are now allowed by invalid-name.

  • pylint no longer emits invalid-name for non-constants found at module level.

    Pylint was considering all module level variables as constants, which is not what PEP 8 is actually mandating.

  • A new check non-ascii-name was added to detect identifiers with non-ASCII characters.

  • Overloaded typing functions no longer trigger no-self-use, unused-argument, missing-docstring and similar checks that assumed that overloaded functions are normal functions.

  • python -m pylint can no longer be made to import files from the local directory.

  • A new command --list-extensions was added.

    This command lists all extensions present in pylint.extensions.

  • Various false positives have been fixed which you can read more about in the Changelog files.

  • Multiple types of string formatting are allowed in logging functions.

The logging-fstring-interpolation message has been brought back to allow multiple types of string formatting to be used. The type of formatting to use is chosen through enabling and disabling messages rather than through the logging-format-style option. The fstr value of the logging-format-style option is not valid.