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1# Copyright 2007 Google, Inc. All Rights Reserved.2# Licensed to PSF under a Contributor Agreement.3 4"""Abstract Base Classes (ABCs) according to PEP 3119."""5 6 7def abstractmethod(funcobj):8    """A decorator indicating abstract methods.9 10    Requires that the metaclass is ABCMeta or derived from it.  A11    class that has a metaclass derived from ABCMeta cannot be12    instantiated unless all of its abstract methods are overridden.13    The abstract methods can be called using any of the normal14    'super' call mechanisms.  abstractmethod() may be used to declare15    abstract methods for properties and descriptors.16 17    Usage:18 19        class C(metaclass=ABCMeta):20            @abstractmethod21            def my_abstract_method(self, ...):22                ...23    """24    funcobj.__isabstractmethod__ = True25    return funcobj26 27 28class abstractclassmethod(classmethod):29    """A decorator indicating abstract classmethods.30 31    Deprecated, use 'classmethod' with 'abstractmethod' instead:32 33        class C(ABC):34            @classmethod35            @abstractmethod36            def my_abstract_classmethod(cls, ...):37                ...38 39    """40 41    __isabstractmethod__ = True42 43    def __init__(self, callable):44        callable.__isabstractmethod__ = True45        super().__init__(callable)46 47 48class abstractstaticmethod(staticmethod):49    """A decorator indicating abstract staticmethods.50 51    Deprecated, use 'staticmethod' with 'abstractmethod' instead:52 53        class C(ABC):54            @staticmethod55            @abstractmethod56            def my_abstract_staticmethod(...):57                ...58 59    """60 61    __isabstractmethod__ = True62 63    def __init__(self, callable):64        callable.__isabstractmethod__ = True65        super().__init__(callable)66 67 68class abstractproperty(property):69    """A decorator indicating abstract properties.70 71    Deprecated, use 'property' with 'abstractmethod' instead:72 73        class C(ABC):74            @property75            @abstractmethod76            def my_abstract_property(self):77                ...78 79    """80 81    __isabstractmethod__ = True82 83 84try:85    from _abc import (get_cache_token, _abc_init, _abc_register,86                      _abc_instancecheck, _abc_subclasscheck, _get_dump,87                      _reset_registry, _reset_caches)88except ImportError:89    from _py_abc import ABCMeta, get_cache_token90    ABCMeta.__module__ = 'abc'91else:92    class ABCMeta(type):93        """Metaclass for defining Abstract Base Classes (ABCs).94 95        Use this metaclass to create an ABC.  An ABC can be subclassed96        directly, and then acts as a mix-in class.  You can also register97        unrelated concrete classes (even built-in classes) and unrelated98        ABCs as 'virtual subclasses' -- these and their descendants will99        be considered subclasses of the registering ABC by the built-in100        issubclass() function, but the registering ABC won't show up in101        their MRO (Method Resolution Order) nor will method102        implementations defined by the registering ABC be callable (not103        even via super()).104        """105        def __new__(mcls, name, bases, namespace, **kwargs):106            cls = super().__new__(mcls, name, bases, namespace, **kwargs)107            _abc_init(cls)108            return cls109 110        def register(cls, subclass):111            """Register a virtual subclass of an ABC.112 113            Returns the subclass, to allow usage as a class decorator.114            """115            return _abc_register(cls, subclass)116 117        def __instancecheck__(cls, instance):118            """Override for isinstance(instance, cls)."""119            return _abc_instancecheck(cls, instance)120 121        def __subclasscheck__(cls, subclass):122            """Override for issubclass(subclass, cls)."""123            return _abc_subclasscheck(cls, subclass)124 125        def _dump_registry(cls, file=None):126            """Debug helper to print the ABC registry."""127            print(f"Class: {cls.__module__}.{cls.__qualname__}", file=file)128            print(f"Inv. counter: {get_cache_token()}", file=file)129            (_abc_registry, _abc_cache, _abc_negative_cache,130             _abc_negative_cache_version) = _get_dump(cls)131            print(f"_abc_registry: {_abc_registry!r}", file=file)132            print(f"_abc_cache: {_abc_cache!r}", file=file)133            print(f"_abc_negative_cache: {_abc_negative_cache!r}", file=file)134            print(f"_abc_negative_cache_version: {_abc_negative_cache_version!r}",135                  file=file)136 137        def _abc_registry_clear(cls):138            """Clear the registry (for debugging or testing)."""139            _reset_registry(cls)140 141        def _abc_caches_clear(cls):142            """Clear the caches (for debugging or testing)."""143            _reset_caches(cls)144 145 146class ABC(metaclass=ABCMeta):147    """Helper class that provides a standard way to create an ABC using148    inheritance.149    """150    __slots__ = ()151