import json


def fav_num():
    file_name = 'favorite_number.json'
    try:
        with open(file_name) as f:
            fav = json.load(f)
    except FileNotFoundError:
        fav = input("Whats you num?")
        with open(file_name, 'w') as f:
            json.dump(fav, f)
            print("We'll remember your num")
    else:
        print("Yay,we remembered it: ", fav)


fav_num()