do not use special method on data class

Documentos > Code Analysis > Static Analysis Rules > do not use special method on data class

This page is not yet available in Spanish. We are working on its translation.
If you have any questions or feedback about our current translation project, feel free to reach out to us!

Metadata

ID: python-best-practices/dataclass-special-methods

Language: Python

Severity: Notice

Category: Best Practices

Description

Data classes (annotated with @dataclass) do not use special methods, such as __init__, __gt__, and others.

Non-Compliant Code Examples

@dataclass
class _Leaf(Generic[T]):
    parent: _Leaf
    value: T

    def __init__(self, value: Optional[T] = None):
        self.value = value
        self.parent = self

    def update(self, value: T):
        self.value = value
        return self

    def __lt__(self, other: _Leaf):
        return repr(self) < repr(other)

    def __gt__(self, other: _Leaf):
        return repr(self) > repr(other)

    # __eq__ should not be used
    def __eq__(self, other: _Leaf):
        return repr(self) == repr(other)

    def __repr__(self):
        return self.value

Compliant Code Examples

@dataclass
class _Leaf(Generic[T]):
    parent: _Leaf
    value: T

    def update(self, value: T):
        self.value = value
        return self

    def __repr__(self):
        return self.value