#
# http://code.activestate.com/recipes/577070-bound-inner-classes/
#
class BoundInnerClass(object):
def __init__(self, cls):
self.cls = cls
def __get__(self, outer, outer_class):
if not outer:
return self.cls
name = self.cls.__name__
if name in outer.__dict__:
return outer.__dict__[name]
decorator_self = self
class Wrapper(decorator_self.cls):
def __init__(self, *args, **kwargs):
decorator_self.cls.__init__(self, outer, *args, **kwargs)
if decorator_self.cls.__repr__ is object.__repr__:
def __repr__(self):
return "".join([
"<",
self.__module__,
".",
self.__class__.__name__,
" object bound to ",
repr(outer),
" at ",
hex(id(self)),
">"])
Wrapper.__name__ = name
setattr(outer, name, Wrapper)
return Wrapper
if __name__ == "__main__":
class Outer(object):
@BoundInnerClass
class Inner(object):
def __init__(self, parent):
self.parent = parent
@BoundInnerClass
class SubclassOfInner(Inner.cls):
def __init__(self, parent):
super(Outer.SubclassOfInner, self).__init__(parent)
outer = Outer()
inner = outer.Inner()
assert outer.Inner == outer.Inner
assert isinstance(inner, outer.Inner)
assert isinstance(inner, Outer.Inner)
subclass = outer.SubclassOfInner()
assert isinstance(subclass, Outer.SubclassOfInner)
assert isinstance(subclass, outer.SubclassOfInner)
assert isinstance(subclass, Outer.Inner)
# Sadly this unexpected behavior must stand.
# "subclass" is an instance of outer.SubclassOfInner,
# which is a subclass of Outer.SubclassOfInner,
# which is a subclass of Outer.Inner. Meanwhile,
# outer.Inner is also a subclass of Outer.Inner.
assert not isinstance(subclass, outer.Inner)
class InnerChild(outer.Inner):
pass
inner_child = InnerChild()
isinstance(inner_child, Outer.Inner)
isinstance(inner_child, InnerChild)
isinstance(inner_child, outer.Inner)
Diff to Previous Revision
--- revision 2 2010-02-26 16:01:00
+++ revision 3 2010-06-19 14:02:24
@@ -1,37 +1,41 @@
+#
+# http://code.activestate.com/recipes/577070-bound-inner-classes/
+#
+
class BoundInnerClass(object):
- def __init__(bound_class, cls):
- bound_class.cls = cls
- bound_class.cache = {}
+ def __init__(self, cls):
+ self.cls = cls
- def __get__(bound_class, outer_instance, outer_class):
- if not outer_instance:
- return bound_class.cls
+ def __get__(self, outer, outer_class):
+ if not outer:
+ return self.cls
- key = id(outer_instance)
- wrapper = bound_class.cache.get(key)
- if wrapper:
- return wrapper
+ name = self.cls.__name__
- class Wrapper(bound_class.cls):
- def __init__(self, *args, **kwargs):
- bound_class.cls.__init__(self, outer_instance, *args, **kwargs)
+ if name in outer.__dict__:
+ return outer.__dict__[name]
- if bound_class.cls.__repr__ is object.__repr__:
- def __repr__(self):
- return "".join([
- "<",
- self.__module__,
- ".",
- self.__class__.__name__,
- " object bound to ",
- repr(outer_instance),
- " at ",
- hex(id(self)),
- ">"])
+ decorator_self = self
+ class Wrapper(decorator_self.cls):
+ def __init__(self, *args, **kwargs):
+ decorator_self.cls.__init__(self, outer, *args, **kwargs)
- Wrapper.__name__ = bound_class.cls.__name__
- bound_class.cache[key] = Wrapper
- return Wrapper
+ if decorator_self.cls.__repr__ is object.__repr__:
+ def __repr__(self):
+ return "".join([
+ "<",
+ self.__module__,
+ ".",
+ self.__class__.__name__,
+ " object bound to ",
+ repr(outer),
+ " at ",
+ hex(id(self)),
+ ">"])
+
+ Wrapper.__name__ = name
+ setattr(outer, name, Wrapper)
+ return Wrapper
if __name__ == "__main__":
class Outer(object):
@@ -44,7 +48,6 @@
def __init__(self, parent):
super(Outer.SubclassOfInner, self).__init__(parent)
-
outer = Outer()
inner = outer.Inner()
assert outer.Inner == outer.Inner
@@ -54,8 +57,14 @@
subclass = outer.SubclassOfInner()
assert isinstance(subclass, Outer.SubclassOfInner)
assert isinstance(subclass, outer.SubclassOfInner)
- assert not isinstance(subclass, outer.Inner) # funny boundary case! sorry!
assert isinstance(subclass, Outer.Inner)
+
+ # Sadly this unexpected behavior must stand.
+ # "subclass" is an instance of outer.SubclassOfInner,
+ # which is a subclass of Outer.SubclassOfInner,
+ # which is a subclass of Outer.Inner. Meanwhile,
+ # outer.Inner is also a subclass of Outer.Inner.
+ assert not isinstance(subclass, outer.Inner)
class InnerChild(outer.Inner):
pass
