Getting container/parent object from within python
Pass a reference to the Bar object, like so:
class Foo(object):
def __init__(self):
self.text = "Hello World" # has to be created first, so Bar.__init__ can reference it
self.bar = Bar(self)
class Bar(object):
def __init__(self, parent):
self.parent = parent
self.newText = parent.text
foo = Foo()
Edit: as pointed out by @thomleo, this can cause problems with garbage collection. The suggested solution is laid out at http://eli.thegreenplace.net/2009/06/12/safely-using-destructors-in-python/ and looks like
import weakref
class Foo(object):
def __init__(self):
self.text = "Hello World"
self.bar = Bar(self)
class Bar(object):
def __init__(self, parent):
self.parent = weakref.ref(parent) # <= garbage-collector safe!
self.newText = parent.text
foo = Foo()
is it possible to get the object, say Foo, that contains another object, Bar, from within Bar itself?
Not "automatically", because the language isn't built like that, and in particular, the language is built such that there is no way to guarantee that Foo exists.
That said, you can always do it explicitly. Attributes, like every other identifier in Python, are just names, not storage space for data; so nothing prevents you from letting the Bar instance have a manually assigned foo
attribute that is a Foo instance, and vice-versa at the same time.