class Person:
    def __init__(self, name, age):
        self.name = name
        self.age = age

person = Person("Alice", 30)
print(person.name, person.age)

class Person:
    def __init__(self, name, age):
        self.name = name
        self.age = age
    
    def __str__(self):
        return f"{self.name}, {self.age} years old"

person = Person("Alice", 30)
print(person)

class Playlist:
    def __init__(self, songs):
        self.songs = songs
    
    def __len__(self):
        return len(self.songs)

playlist = Playlist(["Song1", "Song2", "Song3"])
print(len(playlist))

class ShoppingCart:
    def __init__(self):
        self.items = {}
    
    def __getitem__(self, product):
        return self.items.get(product, 0)
    
    def __setitem__(self, product, quantity):
        self.items[product] = quantity

cart = ShoppingCart()
cart["apple"] = 3
cart["banana"] = 2
print(cart["apple"])

class Countdown:
    def __init__(self, start):
        self.start = start
    
    def __iter__(self):
        return self
    
    def __next__(self):
        if self.start <= 0:
            raise StopIteration
        else:
            self.start -= 1
            return self.start + 1

countdown = Countdown(5)
for num in countdown:
    print(num)

class Multiplier:
    def __init__(self, factor):
        self.factor = factor
    
    def __call__(self, x):
        return x * self.factor

double = Multiplier(2)
result = double(5)
print(result)

class Book:
    def __init__(self, title, author):
        self.title = title
        self.author = author
    
    def __eq__(self, other):
        return self.title == other.title and self.author == other.author
    
    def __ne__(self, other):
        return not self.__eq__(other)

book1 = Book("Python Crash Course", "Eric Matthes")
book2 = Book("Python Crash Course", "Eric Matthes")
print(book1 == book2)

class Logger:
    def __getattr__(self, name):
        print(f"Accessed undefined attribute: {name}")
        return None
    
    def __setattr__(self, name, value):
        print(f"Set attribute: {name} ={value}")
        super().__setattr__(name, value)

logger = Logger()
logger.undefined_attribute  # 觸發(fā) __getattr__
logger.new_attribute = "New Value"  # 觸發(fā) __setattr__

class Timer:
    def __enter__(self):
        self.start_time = time.time()
        return self
    
    def __exit__(self, exc_type, exc_value, traceback):
        self.end_time = time.time()
        elapsed_time = self.end_time - self.start_time
        print(f"Time elapsed: {elapsed_time} seconds")

with Timer() as timer:
    # 執(zhí)行一些耗時(shí)操作
    time.sleep(2)

class MyClass:
    def __del__(self):
        print("Object deleted")

obj = MyClass()
del obj  # 觸發(fā) __del__