shows recursion using function and generator in python

function_and_generator_recursion.py

#!/usr/bin/env python3

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

def get_tree():
    """
        3
       / \
      1   4
     / \   \
    0   2   5
    """
    node_list = [Node(i) for i in range(6)]
    node_list[3].left = node_list[1]
    node_list[3].right = node_list[4]
    node_list[1].left = node_list[0]
    node_list[1].right = node_list[2]
    node_list[4].right = node_list[5]
    return node_list[3]

def recursive(root, f):
    if root is not None:
        recursive(root.left, f)
        f(root)
        recursive(root.right, f)

def generator_v3(root):
    """ for python 3, with 'yield from'
    """
    if root is not None:
        yield from generator_v3(root.left)
        yield root
        yield from generator_v3(root.right)

def generator_v2(root):
    """ for python 2, without 'yield from'
    """
    if root is not None:
        for node in generator_v2(root.left):
            yield node
        yield root
        for node in generator_v2(root.right):
            yield node

def main():
    def f(node):
        print(node.val)
    root = get_tree()
    print('recursive:')
    recursive(root, f)
    print('\ngenerator 2:')
    for node in generator_v2(root):
        f(node)
    print('\ngenerator 3:')
    for node in generator_v3(root):
        f(node)

if __name__ == '__main__':
    main()