Binary Search Tree insertion in Python not returning to console

Question

while learning about BSTs in hackerrank, I came across the following issue.

My classes for the Node and for the Binary Search Tree is defined as follows:

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

class BinarySearchTree:
    def __init__(self):
        self.root = None

    def insert(self,val):
        currentNode = self.root
        if currentNode is None:
            self.root = Node(val)
        elif currentNode.info > val:
            currentNode.left = insert(currentNode.left,val)
        elif currentNode.info < val:
            currentNode.right = insert(currentNode.right,val)
        return currentNode

However, performing a traversal on tree = BinarySearchTree() after using tree.insert(arr[i] over a for loop for some array of integers arr returns no output. The logic seems correct to me, and I suspect that this is due to a difference in type between Node and BST, but I am unsure of how to resolve this.

Edit: below is the full code from hackerrank. The only bit I was able to edit is the insert function.

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

    def __str__(self):
        return str(self.info) 

def preOrder(root):
    if root == None:
        return
    print (root.info, end=" ")
    preOrder(root.left)
    preOrder(root.right)
    
class BinarySearchTree:
    def __init__(self): 
        self.root = None

    def insert(self,val):
        currentNode = self.root
        if currentNode is None:
            self.root = Node(val)
        elif currentNode.info > val:
            currentNode.left = insert(currentNode.left,val)
        elif currentNode.info < val:
            currentNode.right = insert(currentNode.right,val)
        return currentNode

tree = BinarySearchTree()
t = int(input())

arr = list(map(int, input().split()))

for i in range(t):
    tree.insert(arr[i])

preOrder(tree.root)

The given test case was

6
4 2 3 1 7 6

and was supposed to return 4 2 3 1 7 6, but no output was returned.

Edit: made the changes according to the first answer! Now, I have the following week error:

Traceback (most recent call last):
    File “solution.py”, line 40, in <module>
        tree.insert(arr[i])
    File “solution.py”, line 30, in insert
        currentNode.left = insert(currentNode.left,val)
NameError: name ‘insert’ is not defined

Answer 1

i think the problem lies here

def insert(self,val):
    currentNode = self.root
    if currentNode is None:
        currentNode = Node(val)
    elif currentNode.info > val:
        currentNode.left = insert(currentNode.left,val)
    elif currentNode.info < val:
        currentNode.right = insert(currentNode.right,val)
    return currentNode

as you can see you do "insert" the node but you dont assign it, the code block

if currentNode is None:
    currentNode = Node(val) 

should be

if currentNode is None:
    self.root = Node(val)

you keep on trying to traverse a Null tree

EDIT: Its possible that this is not the problem, please provide the full code the create() function is missing from your code but is called

Answer 2

Here's a somewhat shorter version which avoids nested "if" statements and without the "Node" class:

class BinarySearchTree:
    def __init__(self):
        self.info = None
        self.left = None
        self.right = None

    def insert(self,val):
        if self.info is None:
            self.info = val
            self.left = BinarySearchTree()
            self.right = BinarySearchTree()
        elif self.info > val:
            self.left.insert(val)
        elif self.info < val:
            self.right.insert(val)

Answer 3

change your code to

    def insert(self, val, currentNode):

        if self.root is None:
            self.root = Node(val)

        elif currentNode.info > val:
            if currentNode.left is None
                currentNode.left = Node(val)
            else:
                self.insert(val, currentNode.left)

        elif currentNode.info < val:

            if currentNode.right is None
                currentNode.right = Node(val)
            else:
                self.insert(val, currentNode.right)

and call it via

 tree.insert(val,tree.root)