171 lines
5.6 KiB
Python
171 lines
5.6 KiB
Python
# 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.
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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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Similar to abstractmethod.
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Usage:
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class C(metaclass=ABCMeta):
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@abstractclassmethod
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def my_abstract_classmethod(cls, ...):
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...
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'abstractclassmethod' is deprecated. Use 'classmethod' with
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'abstractmethod' instead.
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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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Similar to abstractmethod.
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Usage:
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class C(metaclass=ABCMeta):
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@abstractstaticmethod
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def my_abstract_staticmethod(...):
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...
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'abstractstaticmethod' is deprecated. Use 'staticmethod' with
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'abstractmethod' instead.
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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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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 properties are overridden.
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The abstract properties can be called using any of the normal
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'super' call mechanisms.
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Usage:
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class C(metaclass=ABCMeta):
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@abstractproperty
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def my_abstract_property(self):
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...
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This defines a read-only property; you can also define a read-write
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abstract property using the 'long' form of property declaration:
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class C(metaclass=ABCMeta):
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def getx(self): ...
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def setx(self, value): ...
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x = abstractproperty(getx, setx)
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'abstractproperty' is deprecated. Use 'property' with 'abstractmethod'
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instead.
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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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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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