Python装饰器之类装饰器详解

def my_decorator(func):
    def wrapper(*args, **kwargs):
        print("Something is happening before the function is called.")
        result = func(*args, **kwargs)
        print("Something is happening after the function is called.")
        return result
    return wrapper

@my_decorator
def say_hello(name):
    print(f"Hello, {name}!")

say_hello("Alice")

def class_decorator(cls):
    class WrappedClass(cls):
        def new_method(self):
            print("This is a new method added by the decorator.")
        def existing_method(self)ktXkmwjaC:
            print("This method is overridden by the decorator.")
    return WrappedClass

@class_decorator
class MyClass:
    def existing_method(self):
        print("This method exists in the original class.")

obj = MyClass()
obj.new_method()          # 调用新增的方法
obj.existing_method()     # 调用被重写的方法

import datetime

def add_timestamp(cls):
    class WrappedClass(cls):
        def __init__(self, *args, **kwargs):
            super().__init__(*args, **kwargs)
            self.created_at = datetime.datetime.now()
    return WrappedClass

@add_timestamp
class MyClass:
    def __init__(self, name):
        self.name = name

obj = MyClass("Alice")
print(obj.name)        # 输出: Alice
print(obj.created_at)  # 输出: 对象的创建时间

def require_admin(cls):
    class WrappedClass(cls):
        def admin_method(self, *args, **kwargs):
            if not self.is_admin:
                raise PermissionError("Admin privileges required")
            return super().admin_method(*args, **kwargs)
    return WrappedClass

@require_admin
class MyClass:
 android   def __init__(self, is_admin):
        self.is_admin = is_admin

    def admin_method(self):
        print("This is an admin method.")

admin_obj = MyClass(is_admin=True)
admin_obj.admin_method()  # 正常调用

user_obj = MyClass(is_admin=False)
user_obj.admin_method()   # 抛出 PermissionError

def validate_params(cls):
    class WrappedClass(cls):
        def method_with_validation(self, x):
            if not isinstance(x, int):
                raise ValueError("Parameter x must be an integer")
            return super().method_with_validation(x)
    return WrappedClass

@validate_params
class MyClass:
    def method_with_validation(self, x):
        print(f"Received {x}")

obj = MyClass()
obj.method_with_validation(10)  # 正常调用
obj.method_with_validation("a") # 抛出 ValueError

import datetime

def log_activity(cls):
    class WrappedClass(cls):
        def __getattribute__(self, name):
            attr = super().__getattribute__(name)
            if callable(attr):
                def logged(*args, **kwargs):
                    print(f"Calling {name} with arguments {args} and {kwargs} at {datetime.datetime.now()}")
                    result = attr(*args, **kwargs)
                    print(f"{name} returned {result}")
                    return result
                return logged
            return attr
    return WrappedClass

def require_permission(permission):
    def decorator(cls):
        class WrappedClass(cls):
            def __getattribute__(self, name):
                attr = super().__getattribute__(name)
                if callable(attr):
                    def secured(*args, **kwargs):
                        if not self.has_permission(permission):
                            raise PermissionError(f"Permission {permission} required")
                        return attr(*args, **kwargs)
                    return secured
                return attr
        return WrappedClass
    return decorator

def validate_params(cls):
    class WrappedClass(cls):
        def method_with_validation(sChina编程elf, x):
            if not isinstance(x, int):
                raise ValueError("Parameter x must be an integer")
            return super().method_with_validation(x)
    return WrappedClass

@log_activity
@require_permission("admin")
@validate_params
class MyClass:
    def __init__(self, is_admin):
     android   self.is_admin = is_admin

    def has_permission(self, permission):
        return self.is_admin

    def method_with_validation(self, x):
        return f"Received {x}"

# 测试综合示例
admin_obj = MyClass(is_admin=True)
print(admin_obj.method_with_validation(10))  # 正常调用

try:
    admin_obj.method_with_validation("a")  # 抛出 ValueError
except ValueError as e:
    print(e)

user_obj = MyClass(is_admin=False)
try:
    user_obj.method_with_validation(10)  # 抛出 PermissionError
except PermissionError as e:
    print(e)