httk.core.views.backend

Classes

Backend

Abstract base class to be subclassed into classes that keep track of alternative

Module Contents

class httk.core.views.backend.Backend[BackendT: Backend](backend, **hints)[source]

Bases: abc.ABC

Abstract base class to be subclassed into classes that keep track of alternative representations of certain types of data, all adhering to a common API interface.

The class variable backend_classes is a list of all classes that can carry the kind of data the subclass represents.

A system of “hints” are used primarily to disambiguate between multiple valid interpretations of the same input object. Unless otherwise documented for a specific backend, extra hints that do not affect this interpretation are ignored.

A set of backends are meant to be combined with a set of Views.

Concrete backends implement _backend_adopt to accept an object and return an initialized backend instance, or None to decline it. The kind hint convention is used to disambiguate between multiple valid interpretations.

Parameters:

  • backend (Any) – Source value or backend being adopted by the concrete backend.

  • **hints (Any) – Backend-specific initialization hints.

backend_classes: ClassVar[list[type[Backend[Any]]]][source]
classmethod create(obj, **hints)[source]

Given a source data (obj) and a set of hints, create a backend from one of the alternatives in the class variable backend_classes.

By design this creation depends heavily on order of the classes in backend_classes. Each class is tried in the order they appear until one of them is successful, in the sense that their _backend_adopt returns an initialized instance. Sometimes multiple backend classes can handle the same input type. In that case, dispatch is guided by keyword arguments **hints, with the convention that:

  • if a hint named kind is given, a backend class should accept the object only if it matches that kind;

  • when kind matches, additional unrecognized hints may be ignored.

Parameters:

  • obj (Any) – Source object to represent with a registered backend.

  • **hints (Any) – Backend-selection and disambiguation hints.

Returns:

A backend that represents obj.

Raises:

TypeError – If no registered backend accepts obj and the hints.

Return type:

Self

unwrap()[source]

Return the most raw representation possible of this backend, i.e., if it uses a backend with an internal representaion - or if it can (possibly lossly) convert itself into a more raw representation that still would be recognized as a <Something>Like type, that representation will be returned. If this is not possible, the instance itself is returned.

Returns:

The backend’s most raw available representation.

Return type:

Any