2022-09-17 15:26:13 +03:00
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# Copyright 2007 Google, Inc. All Rights Reserved.
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# Licensed to PSF under a Contributor Agreement.
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"""Abstract Base Classes (ABCs) according to PEP 3119."""
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def abstractmethod(funcobj):
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"""A decorator indicating abstract methods.
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Requires that the metaclass is ABCMeta or derived from it. A
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class that has a metaclass derived from ABCMeta cannot be
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instantiated unless all of its abstract methods are overridden.
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The abstract methods can be called using any of the normal
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'super' call mechanisms. abstractmethod() may be used to declare
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abstract methods for properties and descriptors.
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Usage:
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class C(metaclass=ABCMeta):
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@abstractmethod
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def my_abstract_method(self, ...):
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...
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"""
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funcobj.__isabstractmethod__ = True
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return funcobj
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class abstractclassmethod(classmethod):
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"""A decorator indicating abstract classmethods.
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Deprecated, use 'classmethod' with 'abstractmethod' instead:
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class C(ABC):
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@classmethod
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@abstractmethod
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def my_abstract_classmethod(cls, ...):
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...
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"""
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__isabstractmethod__ = True
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def __init__(self, callable):
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callable.__isabstractmethod__ = True
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super().__init__(callable)
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class abstractstaticmethod(staticmethod):
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"""A decorator indicating abstract staticmethods.
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Deprecated, use 'staticmethod' with 'abstractmethod' instead:
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class C(ABC):
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@staticmethod
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@abstractmethod
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def my_abstract_staticmethod(...):
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...
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"""
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__isabstractmethod__ = True
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def __init__(self, callable):
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callable.__isabstractmethod__ = True
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super().__init__(callable)
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class abstractproperty(property):
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"""A decorator indicating abstract properties.
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Deprecated, use 'property' with 'abstractmethod' instead:
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class C(ABC):
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@property
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@abstractmethod
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def my_abstract_property(self):
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...
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"""
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__isabstractmethod__ = True
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try:
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from _abc import (get_cache_token, _abc_init, _abc_register,
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_abc_instancecheck, _abc_subclasscheck, _get_dump,
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_reset_registry, _reset_caches)
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except ImportError:
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from _py_abc import ABCMeta, get_cache_token
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ABCMeta.__module__ = 'abc'
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else:
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class ABCMeta(type):
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"""Metaclass for defining Abstract Base Classes (ABCs).
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Use this metaclass to create an ABC. An ABC can be subclassed
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directly, and then acts as a mix-in class. You can also register
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unrelated concrete classes (even built-in classes) and unrelated
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ABCs as 'virtual subclasses' -- these and their descendants will
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be considered subclasses of the registering ABC by the built-in
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issubclass() function, but the registering ABC won't show up in
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their MRO (Method Resolution Order) nor will method
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implementations defined by the registering ABC be callable (not
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even via super()).
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"""
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def __new__(mcls, name, bases, namespace, **kwargs):
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cls = super().__new__(mcls, name, bases, namespace, **kwargs)
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_abc_init(cls)
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return cls
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def register(cls, subclass):
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"""Register a virtual subclass of an ABC.
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Returns the subclass, to allow usage as a class decorator.
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"""
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return _abc_register(cls, subclass)
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def __instancecheck__(cls, instance):
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"""Override for isinstance(instance, cls)."""
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return _abc_instancecheck(cls, instance)
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def __subclasscheck__(cls, subclass):
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"""Override for issubclass(subclass, cls)."""
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return _abc_subclasscheck(cls, subclass)
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def _dump_registry(cls, file=None):
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"""Debug helper to print the ABC registry."""
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print(f"Class: {cls.__module__}.{cls.__qualname__}", file=file)
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print(f"Inv. counter: {get_cache_token()}", file=file)
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(_abc_registry, _abc_cache, _abc_negative_cache,
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_abc_negative_cache_version) = _get_dump(cls)
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print(f"_abc_registry: {_abc_registry!r}", file=file)
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print(f"_abc_cache: {_abc_cache!r}", file=file)
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print(f"_abc_negative_cache: {_abc_negative_cache!r}", file=file)
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print(f"_abc_negative_cache_version: {_abc_negative_cache_version!r}",
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file=file)
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def _abc_registry_clear(cls):
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"""Clear the registry (for debugging or testing)."""
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_reset_registry(cls)
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def _abc_caches_clear(cls):
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"""Clear the caches (for debugging or testing)."""
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_reset_caches(cls)
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2022-10-09 16:27:10 +03:00
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def update_abstractmethods(cls):
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"""Recalculate the set of abstract methods of an abstract class.
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If a class has had one of its abstract methods implemented after the
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class was created, the method will not be considered implemented until
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this function is called. Alternatively, if a new abstract method has been
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added to the class, it will only be considered an abstract method of the
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class after this function is called.
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This function should be called before any use is made of the class,
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usually in class decorators that add methods to the subject class.
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Returns cls, to allow usage as a class decorator.
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If cls is not an instance of ABCMeta, does nothing.
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"""
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if not hasattr(cls, '__abstractmethods__'):
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# We check for __abstractmethods__ here because cls might by a C
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# implementation or a python implementation (especially during
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# testing), and we want to handle both cases.
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return cls
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abstracts = set()
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# Check the existing abstract methods of the parents, keep only the ones
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# that are not implemented.
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for scls in cls.__bases__:
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for name in getattr(scls, '__abstractmethods__', ()):
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value = getattr(cls, name, None)
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if getattr(value, "__isabstractmethod__", False):
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abstracts.add(name)
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# Also add any other newly added abstract methods.
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for name, value in cls.__dict__.items():
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if getattr(value, "__isabstractmethod__", False):
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abstracts.add(name)
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cls.__abstractmethods__ = frozenset(abstracts)
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return cls
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2022-09-17 15:26:13 +03:00
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class ABC(metaclass=ABCMeta):
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"""Helper class that provides a standard way to create an ABC using
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inheritance.
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"""
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__slots__ = ()
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