do not use special method on data class

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

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