Skip to content

invalid-index-return-type (PLE0305)

Added in 0.6.0 · Related issues · View source

Derived from the Pylint linter.

What it does

Checks for __index__ implementations that return non-integer values.

Why is this bad?

The __index__ method should return an integer. Returning a different type may cause unexpected behavior.

Note: bool is a subclass of int, so it's technically valid for __index__ to return True or False. However, a DeprecationWarning (DeprecationWarning: __index__ returned non-int (type bool)) for such cases was already introduced, thus this is a conscious difference between the original pylint rule and the current ruff implementation.

Example

class Foo:
    def __index__(self):
        return "2"

Use instead:

class Foo:
    def __index__(self):
        return 2

References