Python 中的装饰器进阶：多个装饰器堆叠

装饰器堆叠时，执行顺序从内到外被装饰，从外到内执行。

def decorator_a(func):
    print('A decorates')
    def wrapper(*args, **kwargs):
        print('A before call')
        result = func(*args, **kwargs)
        print('A after call')
        return result
    return wrapper

def decorator_b(func):
    print('B decorates')
    def wrapper(*args, **kwargs):
        print('B before call')
        result = func(*args, **kwargs)
        print('B after call')
        return result
    return wrapper

@decorator_a
@decorator_b
def say_hello(name):
    print(f'Hello {name}')

# 等价于: say_hello = decorator_a(decorator_b(say_hello))
# 相当于:
# 1. 先 B decorates
# 2. 再 A decorates
# 调用时：A before > B before > Hello > B after > A after

装饰时从下到上，调用时从上到下（洋葱模型）。