cpython/abc.py at 3.8 · python/cpython

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	# 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. abstractmethod() may be used to declare
	abstract methods for properties and descriptors.

	Usage:

	class C(metaclass=ABCMeta):
	@abstractmethod
	def my_abstract_method(self, ...):
	...
	"""
	funcobj.__isabstractmethod__ = True
	return funcobj


	class abstractclassmethod(classmethod):
	"""A decorator indicating abstract classmethods.

	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.

	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.

	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__ = ()