Python装饰器与装饰类详解

在 Python 编程中，装饰器（Decorator）是一种特殊类型的函数，它可以修改其他函数的功能或行为，而无需直接改变这些函数的代码。装饰器通常用于添加功能，如日志记录、性能测试、事务处理等。

### 装饰器示例

import time

def math_type(type='add'):
    def decorator_time(func):
        def wrapper(*args, **kwargs):
            print(f'Operation type: {type}')
            start_time = time.time()
            print(f'Start time: {start_time}')
            result = func(*args, **kwargs)
            end_time = time.time()
            print(f'End time: {end_time}')
            print(f'Total time: {end_time - start_time} seconds')
            return result
        return wrapper
    return decorator_time

@math_type('add')
def add_numbers(*args, **kwargs):
    total = 0
    for num in args:
        total += num
    for key, value in kwargs.items():
        total += value
    return total

@math_type('subtract')
def subtract_numbers(*args, **kwargs):
    total = 0
    for num in args:
        total -= num
    for key, value in kwargs.items():
        total -= value
    return total

# 测试装饰器
result_add = add_numbers(12, 3, a=5, b=3)
print(f'Result of addition: {result_add}')

result_subtract = subtract_numbers(12, 3, a=5, b=3)
print(f'Result of subtraction: {result_subtract}')

### 装饰类示例

装饰类类似于装饰器，但它们用于类而不是函数。装饰类可以在类实例化时添加额外的功能或属性。

def decorate_class(original_class):
    class NewClass:
        def __init__(self, *args, **kwargs):
            self.total_display = 0
            self.wrapped = original_class(*args, **kwargs)

        def display(self):
            self.total_display += 1
            print(f'Total displays: {self.total_display}')
            self.wrapped.display()

    return NewClass

@decorate_class
class Bird:
    def __init__(self, age):
        self.age = age

    def display(self):
        print(f'My age is: {self.age}')

# 创建并测试装饰类
bird_instance = Bird(5)
for _ in range(3):
    bird_instance.display()

通过上述示例，我们可以看到装饰器和装饰类如何在不修改原始代码的情况下，为函数和类添加新的功能。这对于提高代码的可维护性和复用性非常有帮助。