# Copyright 2007 Google, Inc. All Rights Reserved. # Licensed to PSF under a Contributor Agreement. """Abstract Base Classes (ABCs) according to PEP 3119.""" def abstractmethod(funcobj): """A decorator indicating abstract methods. Requires that the metaclass is ABCMeta or derived from it. A class that has a metaclass derived from ABCMeta cannot be instantiated unless all of its abstract methods are overridden. The abstract methods can be called using any of the normal 'super' call mechanisms. Usage: class C(metaclass=ABCMeta): @abstractmethod def my_abstract_method(self, ...): ... """ funcobj.__isabstractmethod__ = True return funcobj class abstractclassmethod(classmethod): """A decorator indicating abstract classmethods. Similar to abstractmethod. Usage: class C(metaclass=ABCMeta): @abstractclassmethod def my_abstract_classmethod(cls, ...): ... 'abstractclassmethod' is deprecated. Use 'classmethod' with 'abstractmethod' instead. """ __isabstractmethod__ = True def __init__(self, callable): callable.__isabstractmethod__ = True super().__init__(callable) class abstractstaticmethod(staticmethod): """A decorator indicating abstract staticmethods. Similar to abstractmethod. Usage: class C(metaclass=ABCMeta): @abstractstaticmethod def my_abstract_staticmethod(...): ... 'abstractstaticmethod' is deprecated. Use 'staticmethod' with 'abstractmethod' instead. """ __isabstractmethod__ = True def __init__(self, callable): callable.__isabstractmethod__ = True super().__init__(callable) class abstractproperty(property): """A decorator indicating abstract properties. Requires that the metaclass is ABCMeta or derived from it. A class that has a metaclass derived from ABCMeta cannot be instantiated unless all of its abstract properties are overridden. The abstract properties can be called using any of the normal 'super' call mechanisms. Usage: class C(metaclass=ABCMeta): @abstractproperty def my_abstract_property(self): ... This defines a read-only property; you can also define a read-write abstract property using the 'long' form of property declaration: class C(metaclass=ABCMeta): def getx(self): ... def setx(self, value): ... x = abstractproperty(getx, setx) 'abstractproperty' is deprecated. Use 'property' with 'abstractmethod' instead. """ __isabstractmethod__ = True try: from _abc import (get_cache_token, _abc_init, _abc_register, _abc_instancecheck, _abc_subclasscheck, _get_dump, _reset_registry, _reset_caches) except ImportError: from _py_abc import ABCMeta, get_cache_token ABCMeta.__module__ = 'abc' else: class ABCMeta(type): """Metaclass for defining Abstract Base Classes (ABCs). Use this metaclass to create an ABC. An ABC can be subclassed directly, and then acts as a mix-in class. You can also register unrelated concrete classes (even built-in classes) and unrelated ABCs as 'virtual subclasses' -- these and their descendants will be considered subclasses of the registering ABC by the built-in issubclass() function, but the registering ABC won't show up in their MRO (Method Resolution Order) nor will method implementations defined by the registering ABC be callable (not even via super()). """ def __new__(mcls, name, bases, namespace, **kwargs): cls = super().__new__(mcls, name, bases, namespace, **kwargs) _abc_init(cls) return cls def register(cls, subclass): """Register a virtual subclass of an ABC. Returns the subclass, to allow usage as a class decorator. """ return _abc_register(cls, subclass) def __instancecheck__(cls, instance): """Override for isinstance(instance, cls).""" return _abc_instancecheck(cls, instance) def __subclasscheck__(cls, subclass): """Override for issubclass(subclass, cls).""" return _abc_subclasscheck(cls, subclass) def _dump_registry(cls, file=None): """Debug helper to print the ABC registry.""" print(f"Class: {cls.__module__}.{cls.__qualname__}", file=file) print(f"Inv. counter: {get_cache_token()}", file=file) (_abc_registry, _abc_cache, _abc_negative_cache, _abc_negative_cache_version) = _get_dump(cls) print(f"_abc_registry: {_abc_registry!r}", file=file) print(f"_abc_cache: {_abc_cache!r}", file=file) print(f"_abc_negative_cache: {_abc_negative_cache!r}", file=file) print(f"_abc_negative_cache_version: {_abc_negative_cache_version!r}", file=file) def _abc_registry_clear(cls): """Clear the registry (for debugging or testing).""" _reset_registry(cls) def _abc_caches_clear(cls): """Clear the caches (for debugging or testing).""" _reset_caches(cls) class ABC(metaclass=ABCMeta): """Helper class that provides a standard way to create an ABC using inheritance. """ __slots__ = ()