Ah thank you for clarifying, I did confuse instance and class
attributes from creating the list in the class def. I actually just
spiffed up that class to represent a portion of a much larger class
that needs getter and setter for children. Doing as you said fixed my
problem, heres the code as reference for w/e
class Widget(object):
_children = None
_parent = None
def __init__(self, parent=None):
self.children = []
self.parent = parent
@property
def children(self):
return self._children
@children.setter
def children(self, obj):
self._children = obj
@property
def parent(self):
return self._parent
@parent.setter
def parent(self, obj):
if obj:
print obj
obj.children.append(self)
self._parent = obj
On Apr 20, 1:05 pm, "Diez B. Roggisch" <de...@nospam.web.de> wrote:
> dasacc22 wrote:
> > Hi,
>
> > I seem to be having a problem with a list being share across multiple
> > instantiations of it and dont quite understand why this is happening.
>
> > My class looks like this,
>
> > class Widget(object):
> > _parent = None
> > _children = []
>
> > def __init__(self, parent=None):
> > self.parent = parent
>
> > @property
> > def children(self):
> > return self._children
>
> > @property
> > def parent(self):
> > return self._parent
>
> > @parent.setter
> > def parent(self, obj):
> > if obj:
> > obj._children.append(self)
> > self._parent = obj
>
> > now if i make instances and attach children like so
>
> > a = Widget()
> > b = Widget(a)
> > c = Widget(a)
> > d = Widget(c)
>
> > Basically all the objects end up sharing the _children list from `a`
> > instead of forming something like a tree. Any advice would be greatly
> > appreciated.
>
> The problem stems from you confusing instance attributes with class
> attributes. You use a latter, which is shared amongst *all* instances of a
> given class.
>
> If you want instance-attributes, use
>
> def __init__(self, ..):
> self.children = []
>
> also, your use of properties for the children is pointless in Python. Just
> use "children" as attribute name. Then, if at one fine day you want to do
> something more than just returning that value, you can still do that witout
> changing the interface by using a property - as you do so for parent.
>
> Diez
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