Fabian Steiner wrote:
> Hello!
>
> I have got a Python "Device" Object which has got a attribute (list)
> called children which my contain several other "Device" objects. I
> implemented it this way in order to achieve a kind of parent/child
> relationship.
>
> Now I would like to get all children of a given "Device" object and
> thought that it would be the best way to use recursive function.
>
> This is what I got so far:
>
> def getAllChildren(self, children=[]):
> if self.children:
> children.extend(self.children)
> for child in self.children:
> child.getAllChildren(children)
> return children
>
> Unfortunately, it doesn't work like expected since the default parameter
> children=[] is evaluated only once. That's why the children list becomes
> larger and larger after calling the method several times but I can't
> think of another possibility.
>
> Do you have any ideas?
This is a standard question, and has a standard answer: replace
def getAllChildren(self, children=[]):
with
def getAllChildren(self, children=None):
if children is None:
children = []
That way a new empty list is created for each call that receives no
"children" argument. Otherwise the same (once-empty) list is used for
them all.
regards
Steve
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