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invalid-first-argument-name-for-class-method (N804)

Added in v0.0.77 · Related issues · View source

Derived from the pep8-naming linter.

Fix is sometimes available.

What it does

Checks for class methods that use a name other than cls for their first argument.

The method __new__ is exempted from this check and the corresponding violation is caught by bad-staticmethod-argument.

Why is this bad?

PEP 8 recommends the use of cls as the first argument for all class methods:

Always use cls for the first argument to class methods.

If a function argument’s name clashes with a reserved keyword, it is generally better to append a single trailing underscore rather than use an abbreviation or spelling corruption. Thus class_ is better than clss. (Perhaps better is to avoid such clashes by using a synonym.)

Names can be excluded from this rule using the lint.pep8-naming.ignore-names or lint.pep8-naming.extend-ignore-names configuration options. For example, to allow the use of klass as the first argument to class methods, set the lint.pep8-naming.extend-ignore-names option to ["klass"].

Example

class Example:
    @classmethod
    def function(self, data): ...

Use instead:

class Example:
    @classmethod
    def function(cls, data): ...

Fix safety

This rule's fix is marked as unsafe, as renaming a method parameter can change the behavior of the program.

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