An binary tree sample implementation (insert, traverse_inorder, traverse_preorder, traverse_postorder included)

binary_tree.py

def binarytree(value):
    return Node(value)


class Node(object):
    
    def __init__(self, value):
        self.__value = value
        self.__left_node = None
        self.__right_node = None

    @property
    def value(self):
        return self.__value

    @property
    def left_node(self):
        return self.__left_node

    @property
    def right_node(self):
        return self.__right_node

    def insert(self, value):
        if value > self.__value:
            if not self.__right_node:
                self.__right_node = Node(value)
                print('inserted {} to the right of {}'.format(value, self.__value))
            else:
                self.__right_node.insert(value)
        else:
            if not self.__left_node:
                self.__left_node = Node(value)
                print('inserted {} to the left of {}'.format(value, self.__value))
            else:
                self.__left_node.insert(value)

    def traverse_inorder(self):
        if self.__left_node:
            self.__left_node.traverse_inorder()
        
        print('node ', self.__value)

        if self.__right_node:
            self.__right_node.traverse_inorder()

    def traverse_preorder(self):
        print('node ', self.__value)
        if self.__left_node:
            self.__left_node.traverse_preorder()
        if self.__right_node:
            self.__right_node.traverse_preorder()

    def traverse_postorder(self):
        if self.__left_node:
            self.__left_node.traverse_postorder()
        if self.__right_node:
            self.__right_node.traverse_postorder()

        print('node ', self.__value)

    def contains(self, value):
        if value > self.__value:
            if self.__right_node:
                return self.__right_node.contains(value)
            else:
                return False
        elif value < self.__value:
            if self.__left_node:
                return self.__left_node.contains(value)
            else:
                return False
        else:
            return True


def run():
    print('------------inserting------------')
    tree = binarytree(3) 
    tree.insert(5)
    tree.insert(7)
    tree.insert(4)
    tree.insert(2)
    tree.insert(1)

    print('')
    print('--------traversing in order------')
    tree.traverse_inorder()

    print('')
    print('-------traversing pre order------')
    tree.traverse_preorder()

    print('')
    print('------traversing post order------')
    tree.traverse_postorder()

    print('')
    print('------contains------')
    print(tree.contains(3))
    print(tree.contains(1))
    print(tree.contains(5))
    print(tree.contains(7))
    print(tree.contains(2))
    print(tree.contains(4))
    print(tree.contains(55))
    print(tree.contains(6))


if __name__ == '__main__':
	run()