Python装饰器

无参数的函数

# -*- coding: utf-8 -*-

from time import ctime, sleep


def timefun(func):
    def wrappedfunc():
        print "%s called at %s" % (func.__name__, ctime())
        func()
    return wrappedfunc


@timefun
def foo():
    print "I am foo"

foo()
sleep(2)
foo()

运行结果

foo called at Fri Aug  4 17:48:31 2017
I am foo
foo called at Fri Aug  4 17:48:33 2017
I am foo

被装饰的函数有参数

# -*- coding: utf-8 -*-

from time import ctime, sleep


def timefun(func):
    def wrappedfunc(a, b):
        print "%s called at %s" % (func.__name__, ctime())
        print a, b
        func(a, b)

    return wrappedfunc


@timefun
def foo(a, b):
    print a + b


foo(3, 5)
sleep(2)
foo(2, 4)

运行

foo called at Fri Aug  4 17:36:22 2017
3 5
8
foo called at Fri Aug  4 17:36:24 2017
2 4
6

被装饰的函数有不定长参数

# -*- coding: utf-8 -*-

from time import ctime, sleep


def timefun(func):
    def wrappedfunc(*args, **kwargs):
        print "%s called at %s"%(func.__name__,ctime())
        func(*args, **kwargs)

    return wrappedfunc


@timefun
def foo(a, b, c):
    print(a + b + c)


foo(3, 5, 7)
sleep(2)
foo(2, 4, 9)

运行结果

foo called at Fri Aug  4 17:52:17 2017
15
foo called at Fri Aug  4 17:52:19 2017
15

装饰器中的return

# -*- coding: utf-8 -*-

from time import ctime, sleep


def timefun(func):
    def wrappedfunc():
        print "%s called at %s" % (func.__name__, ctime())
        func()
    return wrappedfunc


@timefun
def foo():
    print "I am foo"


@timefun
def getInfo():
    return '-----haha-----'


foo()
sleep(2)
foo()

print(getInfo())

运行结果

foo called at Fri Aug  4 17:57:07 2017
I am foo
foo called at Fri Aug  4 17:57:09 2017
I am foo
getInfo called at Fri Aug  4 17:57:09 2017
None

修改装饰器为return func()

# -*- coding: utf-8 -*-

from time import ctime, sleep


def timefun(func):
    def wrappedfunc():
        print "%s called at %s" % (func.__name__, ctime())
        return func()
    return wrappedfunc


@timefun
def foo():
    print "I am foo"


@timefun
def getInfo():
    return "-----haha-----"


foo()
sleep(2)
foo()

print(getInfo())

运行结果

foo called at Fri Aug  4 18:05:04 2017
I am foo
foo called at Fri Aug  4 18:05:06 2017
I am foo
getInfo called at Fri Aug  4 18:05:06 2017
-----haha-----

总结

一般情况下为了让装饰器更通用，可以有return

装饰器带参数,在原有装饰器的基础上，设置外部变量

# -*- coding: utf-8 -*-

from time import ctime, sleep


def timefun_arg(pre="hello"):
    def timefun(func):
        def wrappedfunc():
            print "%s called at %s %s" % (func.__name__, ctime(), pre)
            return func()

        return wrappedfunc

    return timefun


@timefun_arg("matrix")
def foo():
    print "I am foo"


@timefun_arg("python")
def too():
    print "I am too"


foo()
sleep(2)
foo()

too()
sleep(2)
too()

运行结果

foo called at Fri Aug  4 18:11:43 2017 matrix
I am foo
foo called at Fri Aug  4 18:11:45 2017 matrix
I am foo
too called at Fri Aug  4 18:11:45 2017 python
I am too
too called at Fri Aug  4 18:11:47 2017 python
I am too

类装饰器(拓展)

装饰器函数其实是这样一个接口约束，它必须接受一个callable对象作为参数，然后返回一个callable对象。在Python中一般callable对象都是函数，但也有例外。只要某个对象重写了 call() 方法，那么这个对象就是callable的

# -*- coding: utf-8 -*-

class Test():
    def __call__(self):
        print('call me!')

t = Test()
t()  # call me

运行结果

call me!