External Iterators for DFV and BFV in Python

In my post I started a brief discussion on internal interators and external iterators.
Here I show how a couple of external iterators can be implemented in Python using generators.
The code comes from the presentation I gave at Pycon Italia 4.

We are basically assuming a n-tree of nodes where each node has an attribute value where its value is held and an attribute children that is a list (but any iterable is ok) of its children.

def depth_first_visit(node):
    stack = [node, ]
    while stack:
        current_node = stack.pop()
        stack.extend(reversed(current_node.children))
        yield current_node.value
    
def breadth_first_visit(node):
    queue = collections.deque((node, ))
    while queue:
        current_node = queue.popleft()
        queue.extend(current_node.children)
        yield current_node.value