##
## http://code.activestate.com/recipes/577070-bound-inner-classes/
##
##
## Copyright 2010-2011 by Alex Martelli and Larry Hastings
##
## This software is provided 'as-is', without any express or implied
## warranty. In no event will the authors be held liable for any damages
## arising from the use of this software.
##
## Permission is granted to anyone to use this software for any purpose,
## including commercial applications, and to alter it and redistribute it
## freely, subject to the following restrictions:
##
## 1. The origin of this software must not be misrepresented; you must not
## claim that you wrote the original software. If you use this software
## in a product, an acknowledgment in the product documentation would be
## appreciated but is not required.
##
## 2. Altered source versions must be plainly marked as such, and must not be
## misrepresented as being the original software.
##
## 3. This notice may not be removed or altered from any source
## distribution.
##
__all__ = ["BoundInnerClass", "UnboundInnerClass"]
import weakref
class Worker(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 we're already cached in outer, use that version
# (but don't use getattr, that would call __get_ recursively)
if name in outer.__dict__:
return outer.__dict__[name]
wrapper_bases = [self.cls]
# iterate over cls's bases and look in outer to see
# if any have bound inner classes in outer.
# if so, multiply inherit from the bound inner version(s).
multiply_inherit = False
for base in self.cls.__bases__:
# if we can't find a bound inner base,
# add the original unbound base instead.
# this is harmless but helps preserve the original MRO.
inherit_from = base
bound_inner_base = getattr(outer, base.__name__, None)
if bound_inner_base:
attr_bases = getattr(bound_inner_base, "__bases__", (None,))
# the unbound class is always the first base of
# the bound inner class.
if attr_bases[0] == base:
inherit_from = bound_inner_base
multiply_inherit = True
wrapper_bases.append(inherit_from)
Wrapper = self._wrap(outer, wrapper_bases[0])
Wrapper.__name__ = name
if multiply_inherit:
Wrapper.__bases__ = tuple(wrapper_bases)
# cache in outer
setattr(outer, name, Wrapper)
return Wrapper
class BoundInnerClass(Worker):
def _wrap(self, outer, base):
wrapper_self = self
assert outer
outer_weakref = weakref.ref(outer)
class Wrapper(base):
def __init__(self, *args, **kwargs):
wrapper_self.cls.__init__(self, outer_weakref(), *args, **kwargs)
# give the bound inner class a nice repr
# (but only if it doesn't already have a custom repr)
if wrapper_self.cls.__repr__ is object.__repr__:
def __repr__(self):
return "".join([
"<",
self.__module__,
".",
self.__class__.__name__,
" object bound to ",
repr(outer_weakref()),
" at ",
hex(id(self)),
">"])
return Wrapper
class UnboundInnerClass(Worker):
def _wrap(self, outer, base):
class Wrapper(base):
pass
return Wrapper
if __name__ == "__main__":
class Outer(object):
@BoundInnerClass
class Inner(object):
def __init__(self, outer):
self.outer = outer
@BoundInnerClass
class SubclassOfInner(Inner.cls):
def __init__(self, outer):
super(Outer.SubclassOfInner, self).__init__()
assert self.outer == outer
@BoundInnerClass
class SubsubclassOfInner(SubclassOfInner.cls):
def __init__(self, outer):
super(Outer.SubsubclassOfInner, self).__init__()
assert self.outer == outer
@BoundInnerClass
class Subclass2OfInner(Inner.cls):
def __init__(self, outer):
super(Outer.Subclass2OfInner, self).__init__()
assert self.outer == outer
class RandomUnboundInner(object):
def __init__(self):
super(Outer.RandomUnboundInner, self).__init__()
pass
@BoundInnerClass
class MITest(SubclassOfInner.cls, RandomUnboundInner, Subclass2OfInner.cls):
def __init__(self, outer):
super(Outer.MITest, self).__init__()
assert self.outer == outer
@UnboundInnerClass
class UnboundSubclassOfInner(Inner.cls):
pass
def tests():
assert outer.Inner == outer.Inner
assert isinstance(inner, outer.Inner)
assert isinstance(inner, Outer.Inner)
assert isinstance(subclass, Outer.SubclassOfInner)
assert isinstance(subclass, outer.SubclassOfInner)
assert isinstance(subclass, Outer.Inner)
assert isinstance(subclass, outer.Inner)
assert isinstance(subsubclass, Outer.SubsubclassOfInner)
assert isinstance(subsubclass, outer.SubsubclassOfInner)
assert isinstance(subsubclass, Outer.SubclassOfInner)
assert isinstance(subsubclass, outer.SubclassOfInner)
assert isinstance(subsubclass, Outer.Inner)
assert isinstance(subsubclass, outer.Inner)
import itertools
for order in itertools.permutations([1, 2, 3]):
outer = Outer()
for which in order:
if which == 1: inner = outer.Inner()
elif which == 2: subclass = outer.SubclassOfInner()
elif which == 3: subsubclass = outer.SubsubclassOfInner()
tests()
mitest = outer.MITest()
assert outer.MITest.mro() == [
outer.MITest, # bound inner class, notice lowercase-o "outer"
Outer.MITest, # unbound inner class, notice uppercase-o "Outer"
outer.SubclassOfInner, # bound
Outer.SubclassOfInner, # unbound
Outer.RandomUnboundInner, # etc.
outer.Subclass2OfInner,
Outer.Subclass2OfInner,
outer.Inner,
Outer.Inner,
object
]
unbound = outer.UnboundSubclassOfInner()
assert outer.UnboundSubclassOfInner.mro() == [
outer.UnboundSubclassOfInner,
Outer.UnboundSubclassOfInner,
outer.Inner,
Outer.Inner,
object
]
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 4 2011-02-12 19:11:27
+++ revision 5 2011-02-15 00:22:48
@@ -1,8 +1,33 @@
-#
-# http://code.activestate.com/recipes/577070-bound-inner-classes/
-#
-
-__all__ = ["BoundInnerClass", "UnboundInnerSubclass"]
+##
+## http://code.activestate.com/recipes/577070-bound-inner-classes/
+##
+
+##
+## Copyright 2010-2011 by Alex Martelli and Larry Hastings
+##
+## This software is provided 'as-is', without any express or implied
+## warranty. In no event will the authors be held liable for any damages
+## arising from the use of this software.
+##
+## Permission is granted to anyone to use this software for any purpose,
+## including commercial applications, and to alter it and redistribute it
+## freely, subject to the following restrictions:
+##
+## 1. The origin of this software must not be misrepresented; you must not
+## claim that you wrote the original software. If you use this software
+## in a product, an acknowledgment in the product documentation would be
+## appreciated but is not required.
+##
+## 2. Altered source versions must be plainly marked as such, and must not be
+## misrepresented as being the original software.
+##
+## 3. This notice may not be removed or altered from any source
+## distribution.
+##
+
+__all__ = ["BoundInnerClass", "UnboundInnerClass"]
+
+import weakref
class Worker(object):
def __init__(self, cls):
@@ -29,7 +54,7 @@
# if we can't find a bound inner base,
# add the original unbound base instead.
# this is harmless but helps preserve the original MRO.
- parent = base
+ inherit_from = base
bound_inner_base = getattr(outer, base.__name__, None)
if bound_inner_base:
@@ -37,9 +62,9 @@
# the unbound class is always the first base of
# the bound inner class.
if attr_bases[0] == base:
- parent = bound_inner_base
+ inherit_from = bound_inner_base
multiply_inherit = True
- wrapper_bases.append(parent)
+ wrapper_bases.append(inherit_from)
Wrapper = self._wrap(outer, wrapper_bases[0])
Wrapper.__name__ = name
@@ -53,9 +78,11 @@
class BoundInnerClass(Worker):
def _wrap(self, outer, base):
wrapper_self = self
+ assert outer
+ outer_weakref = weakref.ref(outer)
class Wrapper(base):
def __init__(self, *args, **kwargs):
- wrapper_self.cls.__init__(self, outer, *args, **kwargs)
+ wrapper_self.cls.__init__(self, outer_weakref(), *args, **kwargs)
# give the bound inner class a nice repr
# (but only if it doesn't already have a custom repr)
@@ -67,13 +94,13 @@
".",
self.__class__.__name__,
" object bound to ",
- repr(outer),
+ repr(outer_weakref()),
" at ",
hex(id(self)),
">"])
return Wrapper
-class UnboundInnerSubclass(Worker):
+class UnboundInnerClass(Worker):
def _wrap(self, outer, base):
class Wrapper(base):
pass
@@ -84,26 +111,26 @@
class Outer(object):
@BoundInnerClass
class Inner(object):
- def __init__(self, parent):
- self.parent = parent
+ def __init__(self, outer):
+ self.outer = outer
@BoundInnerClass
class SubclassOfInner(Inner.cls):
- def __init__(self, parent):
+ def __init__(self, outer):
super(Outer.SubclassOfInner, self).__init__()
- assert self.parent == parent
+ assert self.outer == outer
@BoundInnerClass
class SubsubclassOfInner(SubclassOfInner.cls):
- def __init__(self, parent):
+ def __init__(self, outer):
super(Outer.SubsubclassOfInner, self).__init__()
- assert self.parent == parent
+ assert self.outer == outer
@BoundInnerClass
class Subclass2OfInner(Inner.cls):
- def __init__(self, parent):
+ def __init__(self, outer):
super(Outer.Subclass2OfInner, self).__init__()
- assert self.parent == parent
+ assert self.outer == outer
class RandomUnboundInner(object):
def __init__(self):
@@ -112,11 +139,11 @@
@BoundInnerClass
class MITest(SubclassOfInner.cls, RandomUnboundInner, Subclass2OfInner.cls):
- def __init__(self, parent):
+ def __init__(self, outer):
super(Outer.MITest, self).__init__()
- assert self.parent == parent
-
- @UnboundInnerSubclass
+ assert self.outer == outer
+
+ @UnboundInnerClass
class UnboundSubclassOfInner(Inner.cls):
pass
