Example of chaining descriptors and sharing a cache between them.

descriptors.py

"""
Example of chaining descriptors and sharing a cache between them.
"""
class LeafDescriptor(object):
    def __get__(self, obj, cls):
        return obj.parent._cache

class Bar(object):
    baz = LeafDescriptor()

    def __init__(self, parent):
        self.parent = parent

class BarDescriptor(object):
    """
    BarDescriptor returns a Bar object.
    """
    def __get__(self, obj, cls):
        return Bar(obj)

class Foo(object):
    _cache = {'empty': None}
    bar = BarDescriptor()

if __name__ == '__main__':
    print Foo().bar.baz