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Diffstat (limited to 'lib/python2.7/abc.py')
| -rw-r--r-- | lib/python2.7/abc.py | 185 |
1 files changed, 0 insertions, 185 deletions
diff --git a/lib/python2.7/abc.py b/lib/python2.7/abc.py deleted file mode 100644 index 02e48a1..0000000 --- a/lib/python2.7/abc.py +++ /dev/null @@ -1,185 +0,0 @@ -# Copyright 2007 Google, Inc. All Rights Reserved. -# Licensed to PSF under a Contributor Agreement. - -"""Abstract Base Classes (ABCs) according to PEP 3119.""" - -import types - -from _weakrefset import WeakSet - -# Instance of old-style class -class _C: pass -_InstanceType = type(_C()) - - -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. - - Usage: - - class C: - __metaclass__ = ABCMeta - @abstractmethod - def my_abstract_method(self, ...): - ... - """ - funcobj.__isabstractmethod__ = True - return funcobj - - -class abstractproperty(property): - """A decorator indicating abstract properties. - - 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 properties are overridden. - The abstract properties can be called using any of the normal - 'super' call mechanisms. - - Usage: - - class C: - __metaclass__ = ABCMeta - @abstractproperty - def my_abstract_property(self): - ... - - This defines a read-only property; you can also define a read-write - abstract property using the 'long' form of property declaration: - - class C: - __metaclass__ = ABCMeta - def getx(self): ... - def setx(self, value): ... - x = abstractproperty(getx, setx) - """ - __isabstractmethod__ = True - - -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()). - - """ - - # A global counter that is incremented each time a class is - # registered as a virtual subclass of anything. It forces the - # negative cache to be cleared before its next use. - _abc_invalidation_counter = 0 - - def __new__(mcls, name, bases, namespace): - cls = super(ABCMeta, mcls).__new__(mcls, name, bases, namespace) - # Compute set of abstract method names - abstracts = set(name - for name, value in namespace.items() - if getattr(value, "__isabstractmethod__", False)) - for base in bases: - for name in getattr(base, "__abstractmethods__", set()): - value = getattr(cls, name, None) - if getattr(value, "__isabstractmethod__", False): - abstracts.add(name) - cls.__abstractmethods__ = frozenset(abstracts) - # Set up inheritance registry - cls._abc_registry = WeakSet() - cls._abc_cache = WeakSet() - cls._abc_negative_cache = WeakSet() - cls._abc_negative_cache_version = ABCMeta._abc_invalidation_counter - return cls - - def register(cls, subclass): - """Register a virtual subclass of an ABC.""" - if not isinstance(subclass, (type, types.ClassType)): - raise TypeError("Can only register classes") - if issubclass(subclass, cls): - return # Already a subclass - # Subtle: test for cycles *after* testing for "already a subclass"; - # this means we allow X.register(X) and interpret it as a no-op. - if issubclass(cls, subclass): - # This would create a cycle, which is bad for the algorithm below - raise RuntimeError("Refusing to create an inheritance cycle") - cls._abc_registry.add(subclass) - ABCMeta._abc_invalidation_counter += 1 # Invalidate negative cache - - def _dump_registry(cls, file=None): - """Debug helper to print the ABC registry.""" - print >> file, "Class: %s.%s" % (cls.__module__, cls.__name__) - print >> file, "Inv.counter: %s" % ABCMeta._abc_invalidation_counter - for name in sorted(cls.__dict__.keys()): - if name.startswith("_abc_"): - value = getattr(cls, name) - print >> file, "%s: %r" % (name, value) - - def __instancecheck__(cls, instance): - """Override for isinstance(instance, cls).""" - # Inline the cache checking when it's simple. - subclass = getattr(instance, '__class__', None) - if subclass is not None and subclass in cls._abc_cache: - return True - subtype = type(instance) - # Old-style instances - if subtype is _InstanceType: - subtype = subclass - if subtype is subclass or subclass is None: - if (cls._abc_negative_cache_version == - ABCMeta._abc_invalidation_counter and - subtype in cls._abc_negative_cache): - return False - # Fall back to the subclass check. - return cls.__subclasscheck__(subtype) - return (cls.__subclasscheck__(subclass) or - cls.__subclasscheck__(subtype)) - - def __subclasscheck__(cls, subclass): - """Override for issubclass(subclass, cls).""" - # Check cache - if subclass in cls._abc_cache: - return True - # Check negative cache; may have to invalidate - if cls._abc_negative_cache_version < ABCMeta._abc_invalidation_counter: - # Invalidate the negative cache - cls._abc_negative_cache = WeakSet() - cls._abc_negative_cache_version = ABCMeta._abc_invalidation_counter - elif subclass in cls._abc_negative_cache: - return False - # Check the subclass hook - ok = cls.__subclasshook__(subclass) - if ok is not NotImplemented: - assert isinstance(ok, bool) - if ok: - cls._abc_cache.add(subclass) - else: - cls._abc_negative_cache.add(subclass) - return ok - # Check if it's a direct subclass - if cls in getattr(subclass, '__mro__', ()): - cls._abc_cache.add(subclass) - return True - # Check if it's a subclass of a registered class (recursive) - for rcls in cls._abc_registry: - if issubclass(subclass, rcls): - cls._abc_cache.add(subclass) - return True - # Check if it's a subclass of a subclass (recursive) - for scls in cls.__subclasses__(): - if issubclass(subclass, scls): - cls._abc_cache.add(subclass) - return True - # No dice; update negative cache - cls._abc_negative_cache.add(subclass) - return False |