Hello Daniel
You've certainly got a lot going on here.
The heart of your question seems to be how a nested (inner) class _a can access
its parent, x. The short answer is that, in Python, it can't without some help.
_a and its instances are unaware of the context in which they are defined, so
they hold no references to x or instance of x. (Technically this is because the
class is not created until after the statements in the class suite are executed)
Before we get to that, though, note that you've made content an attribute of x's
instances, not the x class. So there is no x.content , only inst.content. I'll
assume this was a typo, and you intended inst.content. If this distinction is
mysterious you may want to check: http://docs.python.org/tut/node11.html
Now, back to the question of how instance a could get a reference to inst. The
simplest way to program this is to give it the reference explicitly:
class _a:
def func(self):
"""I would like to do something
with ´content´ here.
"""
print self.__parent__.content
class x:
def __init__(self):
self.content = ["I'm", "self.", "content"]
a = _a()
>>> inst = x()
>>> inst.a.__parent__ = inst # give inst.a a reference to its parent
>>> inst.a.func()
["I'm", 'self.', 'content']
>>>
There is a way to automate "inst.a.__parent__ = inst", although it's not ideal
"getting starting with Python objects" material. The solution is to have _a
implement the descriptor protocol (see:
http://users.rcn.com/python/download/Descriptor.htm), and make the classes
"new-style", i.e., derived from 'object':
class _a(object):
## def __call__(self, v): Method is irrelevant to this discussion
## print v
def func(self):
"""I would like to do something
with ´content´ here.
"""
print self.__parent__.content
def __get__(self, obj, cls):
"""Store a reference to the referring obj"""
if isinstance(obj, cls):
self.__parent__ = obj
return self
class x(object):
def __init__(self):
self.content = ["I'm", "self.", "content"]
a = _a()
>>> inst = x()
>>> inst.a.func() #no need to set inst.a.__parent__ = inst manually now
["I'm", 'self.', 'content']
>>>
HTH
Michael
Thanks for the detailed answer, and yes, it was a typo, I meant
inst = x()
inst.a(5)
inst.a.func()
Following your example I could put together exactly what I wanted, thank you very much.
Daniel
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