BST Insert not working properly in Python

Question

I'm implementing a BST in Python but I have issues with but_insert(t, k). Basically if I just add children to the root, like below, it works:

T = Node(7)
bst_insert(T, 9)
bst_insert(T, 5)

But if I insert another key, then an entire branch from the root seems to be dropped. For instance, if I execute:

T = Node(7)
bst_insert(T, 9)
bst_insert(T, 5)
bst_insert(T, 3)

Then when I print T in order I only get 7 9.

Here is the Node constructor and bst_insert (the print_in_order function works properly so I did not include it).

class Node:
    def __init__(self, key):
        self.key = key
        self.left = None
        self.right = None


def bst_insert(t, k):
    if t is None:
        t = Node(k)

    elif k <= t.key:
        if t.left is None:
            t.left = Node(k)
        else:
            t.left = bst_insert(t.left, k)
    else:
        if t.right is None:
            t.right = Node(k)
        else:
            t.right = bst_insert(t.right, k)

Thanks.

Answer 1

    class Node:
        def __init__(self, key):
            self.key = key
            self.left = None
            self.right = None


    def bst_insert(t, k):
        if t is None:
            t = Node(k)

        elif k <= t.key:
            if t.left is None:
                t.left = Node(k)
            else:
                t.left = bst_insert(t.left, k) #1
        else:
            if t.right is None:
                t.right = Node(k)
            else:
                t.right = bst_insert(t.right, k) #2
        # return the node, #1 and #2 will always get None value
        return t