import pickle
import os

class Node:
    def __init__(self, question=None, animal=None):
        self.question = question
        self.animal = animal
        self.yes = None
        self.no = None

    def is_leaf(self):
        return self.animal is not None

def ask_yes_no(prompt):
    while True:
        ans = input(prompt + ” (y/n): “).strip().lower()
        if ans in [‘y’, ‘yes’]:
            return True
        elif ans in [‘n’, ‘no’]:
            return False
        print(“Please enter y or n.”)

def play(node):
    if node.is_leaf():
        if ask_yes_no(f”Is it a {node.animal}?”):
            print(“Yay! I guessed it!”)
            return node
        else:
            return learn(node)
    else:
        if ask_yes_no(node.question):
            node.yes = play(node.yes)
        else:
            node.no = play(node.no)
        return node

def learn(old_node):
    new_animal = input(“I give up! What animal were you thinking of? “).strip()
    question = input(f”Give me a yes/no question to tell a {new_animal} from a {old_node.animal}: “).strip()
    if ask_yes_no(f”For a {new_animal}, what is the answer to your question?”):
        new_node = Node(question=question)
        new_node.yes = Node(animal=new_animal)
        new_node.no = old_node
    else:
        new_node = Node(question=question)
        new_node.no = Node(animal=new_animal)
        new_node.yes = old_node
    print(“Thanks! I’ll remember that.”)
    return new_node

def save_tree(tree, filename=”animal_tree.pkl”):
    with open(filename, “wb”) as f:
        pickle.dump(tree, f)

def load_tree(filename=”animal_tree.pkl”):
    if os.path.exists(filename):
        with open(filename, “rb”) as f:
            return pickle.load(f)
    else:
        # Start with a default animal
        return Node(animal=”cat”)

def main():
    print(“Think of an animal, and I’ll try to guess it!”)
    tree = load_tree()
    tree = play(tree)
    save_tree(tree)

if __name__ == “__main__”:
    while True:
        main()
        if not ask_yes_no(“Play again?”):
            break