self-or-cls-assignment (PLW0642)

Derived from the Pylint linter.

This rule is unstable and in preview. The --preview flag is required for use.

What it does

Checks for assignment of self and cls in instance and class methods respectively.

Why is this bad?

The identifiers self and cls are conventional in Python for the first argument of instance methods and class methods, respectively.

Example

class Versions:
    def add(self, version):
        self = version

    @classmethod
    def from_list(cls, versions):
        cls = versions

Use instead:

class Versions:
    def add(self, version):
        self.versions.append(version)

    @classmethod
    def from_list(cls, versions):
        return cls(versions)