python的装饰器

装饰器

# 装饰器，特性，注解
# 对修改是封闭的，对扩展是开发的
import time

def print_current_time(func):
    print(time.time())
    func()

def f1():
    print('This is a function-1')

def f2():
    print('This is a function-2')

print_current_time(f1)
print_current_time(f2)

#输出结果
#1521624272.8735173
#This is a function-1
#1521624272.992277
#This is a function-2

不修改函数调用方式，依旧可以修改输出

# 对修改是封闭的，对扩展是开发的
import time

def decorator(func):
    def wrapper():
        print(time.time())
        func()
    return wrapper

@decorator
def f1():
    print('This is a function-1')
def f2():
    print('This is a function-2')

f1()
f2()

#输出结果
#1521637627.8076153
#This is a function-1
#This is a function-2

利用 *args 可以传入任意个参数

# 对修改是封闭的，对扩展是开发的
import time

def decorator(func):
    def wrapper(*args):
        print(time.time())
        func(*args)
    return wrapper

@decorator
def f0():
    print('This is a function-0 ')

@decorator
def f1(func_name):
    print('This is a function-1 ' + func_name)

@decorator
def f2(func_name1, func_name2):
    print('This is a function-2 ' + func_name1)
    print('This is a function-2 ' + func_name2)

f0()
f1('test')
f2('try', 'try')

#输出结果
#1521639444.4680157
#This is a function-0
#1521639444.4700003
#This is a function-1 test
#1521639444.4730039
#This is a function-2 try
#This is a function-2 try

装饰器的最终形态，**kw 代表关键字参数，多余的关键字会被当作字典打印出来

def decorator(func):
    def wrapper(*args, **kw):
        print(time.time())
        func(*args, **kw)
    return wrapper

不破坏代码实现，实现代码复用性，可以多个装饰器堆叠使用