Error in Binary Tree Implementation in Python

Question

I am required to write a class for Node and Binary Tree, both of which work perfectly fine. I'm also required to use a menu for the methods, when I try to add something, it adds but immediately resets to None and starts over again when add is called. This is the menu implementation.

if __name__ == '__main__':

    print("Menu \n"
        "\n"
        "1. Add item \n"
        "2. Get item \n"
        "3. Print Binary Tree in Inorder Transversal \n"
        "4. Exit \n")

    user_input = input("Please select an action from the menu: ")
    tree = BinaryTree()

    if user_input == "1":
        item = str(input("Please enter an item to add to the Binary Tree: "))
        bin_str = str(input("Please enter binary string to place in the Binary Tree: "))
        tree.add(item, bin_str)
        tree.print_inorder()

    elif user_input == "2":
        get_item = input("Please enter binary string of wanted item: ")
        get_bin_str = tree.get(get_item)
        print(get_bin_str)

    elif user_input == "3":
        tree.print_inorder())

    elif user_input == "4":
        sys.exit(0)

    else:
        print("Error: please select an action from the menu")

What do you mean 'it resets to None and starts over again' ? — polku
– polku, Commented May 23, 2016 at 16:10
The code you've shown will run only once irrespective of the input you provide since there is no loop. Assuming you put the loop, make sure to move the tree = BinaryTree() outside the menu as you dont want to reinitialize it everytime . Otherwise it will be losing its state. — algrebe
– algrebe, Commented May 23, 2016 at 16:30

Jenner Felton · Accepted Answer · 2016-05-23 18:09:00Z

As an above comment suggests, you need a while loop to allow for additional user input, without resetting the tree variable each time.

if __name__ == '__main__':

    tree = BinaryTree()
    while True:

        print("Menu \n"
            "\n"
            "1. Add item \n"
            "2. Get item \n"
            "3. Print Binary Tree in Inorder Transversal \n"
            "4. Exit \n")

        user_input = input("Please select an action from the menu: ")

        if user_input == "1":
            item = str(input("Please enter an item to add to the Binary Tree: "))
            bin_str = str(input("Please enter binary string to place in the Binary Tree: "))
            tree.add(item, bin_str)
            tree.print_inorder()

        elif user_input == "2":
            get_item = input("Please enter binary string of wanted item: ")
            get_bin_str = tree.get(get_item)
            print(get_bin_str)

        elif user_input == "3":
            tree.print_inorder())

        elif user_input == "4":
            sys.exit(0)

        else:
            print("Error: please select an action from the menu")

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