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Python Compiled Bytecode | 2009-11-11 | 6KB | 163 lines

# Source Generated with Decompyle++
# File: in.pyc (Python 2.6)

'''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 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()).

    """
    _abc_invalidation_counter = 0

    def __new__(mcls, name, bases, namespace):
        cls = super(ABCMeta, mcls).__new__(mcls, name, bases, namespace)
        abstracts = set((lambda .0: for name, value in .0:
if getattr(value, '__isabstractmethod__', False):
namecontinue)(namespace.items()))
        for base in bases:
            for name in getattr(base, '__abstractmethods__', set()):
                value = getattr(cls, name, None)
                if getattr(value, '__isabstractmethod__', False):
                    abstracts.add(name)
                    continue


        cls.__abstractmethods__ = frozenset(abstracts)
        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')
        isinstance(cls, type)
        if issubclass(subclass, cls):
            return None
        if issubclass(cls, subclass):
            raise RuntimeError('Refusing to create an inheritance cycle')
        issubclass(cls, subclass)
        cls._abc_registry.add(subclass)
        ABCMeta._abc_invalidation_counter += 1


    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)
                continue



    def __instancecheck__(cls, instance):
        '''Override for isinstance(instance, cls).'''
        subclass = getattr(instance, '__class__', None)
        if subclass in cls._abc_cache:
            return True
        subtype = type(instance)
        return subclass is None if subtype is subclass or subclass is None else cls.__subclasscheck__(subtype)


    def __subclasscheck__(cls, subclass):
        '''Override for issubclass(subclass, cls).'''
        if subclass in cls._abc_cache:
            return True
        if cls._abc_negative_cache_version < ABCMeta._abc_invalidation_counter:
            cls._abc_negative_cache = set()
            cls._abc_negative_cache_version = ABCMeta._abc_invalidation_counter
        elif subclass in cls._abc_negative_cache:
            return False
        ok = cls.__subclasshook__(subclass)
        if ok is not NotImplemented:
            if not isinstance(ok, bool):
                raise AssertionError
            if ok:
                cls._abc_cache.add(subclass)
            else:
                cls._abc_negative_cache.add(subclass)
            return ok
        if cls in getattr(subclass, '__mro__', ()):
            cls._abc_cache.add(subclass)
            return True
        for rcls in cls._abc_registry:
            if issubclass(subclass, rcls):
                cls._abc_cache.add(subclass)
                return True

        for scls in cls.__subclasses__():
            if issubclass(subclass, scls):
                cls._abc_cache.add(subclass)
                return True

        cls._abc_negative_cache.add(subclass)
        return False