abc.py

# Copyright 2007 Google, Inc. All Rights Reserved.
# Licensed to PSF under a Contributor Agreement.

"""Abstract Base Classes (ABCs) according to PEP 3119."""


defabstractmethod(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, arg1, arg2, argN):
 ...
 """
funcobj.__isabstractmethod__=True
returnfuncobj


classabstractclassmethod(classmethod):
"""A decorator indicating abstract classmethods.

 Deprecated, use 'classmethod' with 'abstractmethod' instead:

 class C(ABC):
 @classmethod
 @abstractmethod
 def my_abstract_classmethod(cls, ...):
 ...

 """

__isabstractmethod__=True

def__init__(self, callable):
callable.__isabstractmethod__=True
super().__init__(callable)


classabstractstaticmethod(staticmethod):
"""A decorator indicating abstract staticmethods.

 Deprecated, use 'staticmethod' with 'abstractmethod' instead:

 class C(ABC):
 @staticmethod
 @abstractmethod
 def my_abstract_staticmethod(...):
 ...

 """

__isabstractmethod__=True

def__init__(self, callable):
callable.__isabstractmethod__=True
super().__init__(callable)


classabstractproperty(property):
"""A decorator indicating abstract properties.

 Deprecated, use 'property' with 'abstractmethod' instead:

 class C(ABC):
 @property
 @abstractmethod
 def my_abstract_property(self):
 ...

 """

__isabstractmethod__=True


try:
from_abcimport (get_cache_token, _abc_init, _abc_register,
_abc_instancecheck, _abc_subclasscheck, _get_dump,
_reset_registry, _reset_caches)
exceptImportError:
from_py_abcimportABCMeta, get_cache_token
ABCMeta.__module__='abc'
else:
classABCMeta(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)
returncls

defregister(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)


defupdate_abstractmethods(cls):
"""Recalculate the set of abstract methods of an abstract class.

 If a class has had one of its abstract methods implemented after the
 class was created, the method will not be considered implemented until
 this function is called. Alternatively, if a new abstract method has been
 added to the class, it will only be considered an abstract method of the
 class after this function is called.

 This function should be called before any use is made of the class,
 usually in class decorators that add methods to the subject class.

 Returns cls, to allow usage as a class decorator.

 If cls is not an instance of ABCMeta, does nothing.
 """
ifnothasattr(cls, '__abstractmethods__'):
# We check for __abstractmethods__ here because cls might by a C
# implementation or a python implementation (especially during
# testing), and we want to handle both cases.
returncls

abstracts=set()
# Check the existing abstract methods of the parents, keep only the ones
# that are not implemented.
forsclsincls.__bases__:
fornameingetattr(scls, '__abstractmethods__', ()):
value=getattr(cls, name, None)
ifgetattr(value, "__isabstractmethod__", False):
abstracts.add(name)
# Also add any other newly added abstract methods.
forname, valueincls.__dict__.items():
ifgetattr(value, "__isabstractmethod__", False):
abstracts.add(name)
cls.__abstractmethods__=frozenset(abstracts)
returncls


classABC(metaclass=ABCMeta):
"""Helper class that provides a standard way to create an ABC using
 inheritance.
 """
__slots__= ()