>>>>> "Bart" == Bart Van Loon <[EMAIL PROTECTED]> writes:
>> Such an operation will be O(N**2), Bart> why is that? The a[:] operation makes a copy of a (as will the x = a + [n] idiom). Bart> I am building a binary tree where each node is a list. the two Bart> children are the parent list + 1 and the parent list + 2. You might consider creating each node as left = [parent, 1] right = [parent, 2] You thus wind up with a nested set of two-element nodes, e.g.: [] [[], 1] [[], 2] [[[], 1], 1] [[[], 1], 2] [[[], 2], 1] [[[], 2], 2] where the left-hand side of each node is just a reference to the parent node. Once the tree is built if you can flatten the resulting node lists to generate lists which are more efficient for direct element access. Again, this all depends on how big your trees are, what you do with them once they are built, if you need to search the tree while building the tree, etc. Skip -- http://mail.python.org/mailman/listinfo/python-list