Python generator traverse a tree

Question

I am new to Python generator. Here I want to do a post-order traversal of a tree. I found others' codes as follows. I don't quite understand it, instead, I wanted write it simply as the latter. So could anybody tell me why I was wrong?

def _loopallchildren(parent):
    for child in parent.children:
        if child.children:
            for subchild in _loopallchildren(child):
                yield subchild
        yield child

wrong codes:

def _loopallchildren(parent):
    for child in parent.children:
        if child.children:
            _loopallchildren(child)
        yield child

Answer 1

For the same reason that merely calling _loopallchildren(root) from the outside without doing anything with it doesn't do anything. You have to iterate over the generator to make use of it.

In Python ≥ 3.3 you can use yield from _loopallchildren(child) .