Thank you for your reply, but I have question about your code. Your defined:
def post_order(self):
for child in self.childs:
yield child
yield self
just for "Node" , not for "Tree", and do
w("doing generator post_order...")
_t = datetime.now()
for item in root.post_order():
fake = item.value
w("done\n")
w(datetime.now() - _t)
w("\n")
what give us only iterating along root's children, not iterating along
tree...Or I didn't catch your though?
Best Regards
Alex
2011/1/14 kost BebiX <k...@ya.ru>
> 14.01.2011, 14:15, "Alex Boyko" <alex.kyr...@gmail.com>:
> > Dear All!
> >
> > I have deal with large unbalanced trees and I have to implement
> post-order tree traversal. My first attempt is shown below ("Node" and
> "Tree" classes) and based on recursive generators approach.
> >
> > class Node():
> > def __init__(self,value):
> > self.childs = []
> > self.value = value
> >
> > class Tree():
> >
> > def __init__(self, root):
> > self.root = root
> > self.numberCells = 1
> >
> > def add(self, node, child):
> > node.childs.append(child)
> > self.numberCells+=1
> >
> > def __iter__(self):
> > return self.postorder(self.root)
> >
> > def postorder(self, node):
> > if node:
> > for child in node.childs:
> > for n in self.postorder(child):
> > yield n
> > yield node
> >
> > It works fine for small test trees. But, my tree has approximately 300000
> nodes, and shown post order traversal with generators takes 80 sec against 1
> sec with simple recursive routine:
> >
> > def recursiveFromTop(node):
> > for child in node.childs:
> > recursiveFromTop(child)
> > ## here I can do some computations with current node's data
> >
> > So, I'd like to know how should I implement (if it's possible of course)
> __iter__ for my tree class based on recursion without generators? Please,
> can You show me the ways?
> > because I'm very passionate in idea iterate through my tree with simple:
> >
> > for node in tree:
> > do something with node
> >
> > Thanks in Advance!
> > Best Regards!
> > Alex
> >
> > --
> > http://mail.python.org/mailman/listinfo/python-list
>
> Well, I think it's actually because the difference is that you would not do
> yielding, you would just put everything in memory and then return it.
>
> ret_val = [x for x in self.postorder(child)]
> return ret_val + [self]
>
> or something like that (but beware of memory). But that's strange. This
> code works fast:
>
> #!/usr/bin/env python
> # -*- coding: utf-8 -*-
>
> import sys
>
> def w(s):
> sys.stdout.write("%s" % s)
> sys.stdout.flush()
>
> class Node():
> __slots__ = ('childs', 'value',)
>
> def __init__(self, value):
> self.childs = []
> self.value = value
>
> def post_order(self):
> for child in self.childs:
> yield child
> yield self
>
> def build_tree():
> def append_1000_childs(node):
> for i in xrange(20):
> node.childs.append(Node(10))
>
> def append_n_levels(node, levels=1):
> if levels >= 1:
> append_1000_childs(node)
> if levels > 1:
> for child in node.childs:
> append_n_levels(child, levels - 1)
>
> root = Node(10)
> append_n_levels(root, 5)
> return root
>
> if __name__ == '__main__':
> from datetime import datetime
>
> w("building tree...")
> _t = datetime.now()
> root = build_tree()
> w("done\n")
> w(datetime.now() - _t)
> w("\n")
>
> w("doing generator post_order...")
> _t = datetime.now()
> for item in root.post_order():
> fake = item.value
> w("done\n")
> w(datetime.now() - _t)
> w("\n")
>
> def post_order(root):
> for child in root.childs:
> post_order(child)
> fake = item.value
>
> w("doing non-generator post_order...")
> _t = datetime.now()
> post_order(root)
> w("done\n")
> w(datetime.now() - _t)
> w("\n")
>
> $ python postorder.py
> building tree...done
> 0:01:34.422288
> doing generator post_order...done
> 0:00:00.000018
> doing non-generator post_order...done
> 0:00:01.232272
>
> --
> jabber: k...@ya.ru
>
--
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