AttributeError: “instance has no attribute”

Question

I am having a problem understanding why my code gives me this error

AttributeError: "Tree instance has no attribute 'root'"

I am trying to implement a binary search tree and here is my code.

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

class Tree:

    def __init__(self, val):
        root = Node(val)

def main():
    tree = Tree(100);
    print tree.root.val

if __name__ == "__main__":
    main()

I am new to python. Please let me know what is wrong with my code.

Answer 1

You should use self.root to tell the interpreter that the Tree class has a instance var named root .

class Tree:
    def __init__(self, val):
        self.root = Node(val)