--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/symbian-qemu-0.9.1-12/python-2.6.1/Lib/abc.py Fri Jul 31 15:01:17 2009 +0100
@@ -0,0 +1,171 @@
+# Copyright 2007 Google, Inc. All Rights Reserved.
+# Licensed to PSF under a Contributor Agreement.
+
+"""Abstract Base Classes (ABCs) according to PEP 3119."""
+
+
+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 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 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 = set()
+ cls._abc_cache = set()
+ cls._abc_negative_cache = set()
+ 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(cls, type):
+ 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 in cls._abc_cache:
+ return True
+ subtype = type(instance)
+ 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 = set()
+ 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