dataclass

Dataclass is a Python construct that provides a decorator and helper functions for creating classes intended primarily for storing data. It automates common boilerplate tasks by generating methods such as init, repr, and eq, and, if requested, ordering methods. Introduced in Python 3.7 as part of the dataclasses module, it can also be backported to earlier versions via a separate package.

Usage: declare a class with type-annotated attributes and apply @dataclass. Fields with defaults must follow non-default fields. Default values are shared across instances, so use default_factory for mutable types like list or dict. Per-field behavior can be customized with field(), which can set default, default_factory, init, repr, compare, metadata, or exclude a field from certain generated methods. Class-level options include init, repr, eq, order, frozen, and post-init validation via post_init.

Dataclasses provide helpful utilities such as asdict() and astuple() to convert instances to dictionaries or tuples, and replace() to create a copy with some fields altered. They pair well with type hints and support inheritance.

Limitations: dataclasses rely on type annotations and simple storage patterns; they are not a full object system replacement. Complex invariants should be enforced in post_init, and mutable fields require careful handling to avoid shared state. Although frozen dataclasses prevent attribute reassignment, they can still contain mutable objects that may be modified in place.