def num_nodes(tree):
    """Determine the number of nodes in a tree"""
    if tree.is_leaf:
        return 1
    else:
        return 1 + num_nodes(tree.left_child) + num_nodes(tree.right_child)
def num_nodes ( tree ) : if tree . is_leaf : return 1 else : return 1 + num_nodes ( tree . left_child ) + num_nodes ( tree . right_child )
Determine the number of nodes in a tree