Re: Recursive function returning a list
- From: Steve Holden <steve@xxxxxxxxxxxxx>
- Date: Mon, 17 Jul 2006 18:43:34 +0100
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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