装饰器(decorator)

python学习笔记

基于函数的decorator

def decorator(F):
    def new_F(a, b):
        print('input:', a, b)
        return F(a, b)
    return new_F
@decorator
def square_sum(a, b):
    return a**2 + b** 2
@decorator
def square_diff(a, b):
    return a**2 - b** 2
print(square_sum(3, 4))
print(square_diff(3, 4))

运行

/usr/bin/python3.4
input: 3 4
25
input: 3 4
-7

当然也可以两个装饰器一起使用
函数的执行顺序由@decorator的顺序决定

def decorator(F):
    def new_F(a, b):
        print('input:', a, b)
        return F(a, b)
    return new_F
def decorator1(F):
    def new_F(a, b):
        print('This is key')
        return F(a, b)
    return new_F
@decorator
@decorator1
def square_sum(a, b):
    return a**2 + b** 2
@decorator1
@decorator
def square_diff(a, b):
    return a**2 - b** 2
print(square_sum(3, 4))
print(square_diff(3, 4))

运行

/usr/bin/python3.4
This is key
input: 3 4
25
input: 3 4
This is key
-7

带参数的decorator

#新的包装层
def pre_str(pre=''):
    #以前的decorator
    def decorator(F):
        def new_F(a, b):
            print(pre + ' :input', a, b)
            return F(a, b)
        return new_F
    return decorator
@pre_str('Lambda')
def square_sum(a, b):
    return a**2 + b**2
@pre_str('Alpha')
def square_diff(a, b):
    return a**2 - b**2
print(square_sum(3, 4))
print(square_diff(3, 4))

运行

/usr/bin/python3.4
Lambda :input 3 4
25
Alpha :input 3 4
-7

装饰类

跳过

def decorator(aClass):
    class newClass:
        def __init__(self, age):
            self.total_display   = 0
            self.wrapped         = aClass(age)
        def display(self):
            self.total_display += 1
            print("total display", self.total_display)
            self.wrapped.display()
    return newClass
@decorator
class Bird:
    def __init__(self, age):
        self.age = age
    def display(self):
        print("My age is",self.age)
eagleLord = Bird(5)
for i in range(3):
    eagleLord.display()

参考来源

Vamei Python快速教程