Tree insertion and variable referencing

[hshivaraj]

Hey all!
This is probably very basic for some people , but i really cant get my head around this.

The code below performs binary tree insertion. The thing i cant understand is, you'll notice in the _insert function return root. I really dont see the point of that return. However with out that return root. The tree doesn't parse. But however in the calling function insert i dont assign that returned value from _insert to anything. Yet its required. Please help me understand this?

    def insert(self, val):
        if self.root is None:
            self.root = Node(val)
        else:
            self._insert(self.root, val)

    def _insert(self, root, val):
        print(id(root))
        if root is None:
            return Node(val)
        if val <= root.val:
            root.left = self._insert(root.left, val)
        else:
            root.right = self._insert(root.right, val)
        return root