Simple breadth first search on a graph

graph_bfs.py

 def bfs(self, start_node_num):
        """An iterative implementation of Breadth First Search
        iterating through a node's edges."""
        node = self.find_node(start_node_num)
        self._clear_visited()
        ret_list = []
        # Your code here
        queue = [node]
        node.visited = True
        def enqueue(n, q=queue):
            n.visited = True
            q.append(n)
        def unvisited_outgoing_edge(n, e):
            return ((e.node_from.value == n.value) and
                    (not e.node_to.visited))
        while queue:
            node = queue.pop(0)
            ret_list.append(node.value)
            for e in node.edges:
                if unvisited_outgoing_edge(node, e):
                    enqueue(e.node_to)
        return ret_list