Python 无参数和带参数的decorator

无参数的decorator

def performance(f):

    def fn(*args,**kw):

        t1 = time.time()

        r = f(*args,**kw)

        t2 = time.time()

        print 'call %s() in %fs' %(f.__name__,(t2-t1))

        return r

    return fn

@performance

def factorial(n):

    return reduce(lambda x,y: x*y, range(1, n+1))

print factorial(10)

输出结果：

call factorial() in 0.000336s

3628800

带参数的decorator

import time

def performance(unit):

    def perf_decorator(f):

            def wrapper(*args,**kw):

                t1 = time.time()

                r = f(*args,**kw)

                t2 = time.time()

                t = t2-t1

                if unit != 'ms':

                    t = t*1000

                print 'call %s in %f%s'%(f.__name__,t,unit)

                return r

            return wrapper

    return perf_decorator

        

@performance('ms')

def factorial(n):

    return reduce(lambda x,y: x*y, range(1, n+1))

print factorial(10)

输出结果：

call factorial in 0.000332ms

3628800

理解执行顺序：

#perforance('ms')(factorial)

先调用第一层decorator 得到return 是perf_decorator(f) 这个函数

然后再将factorial 传入到f中得到修饰

完善decorator

import time, functools

def performance(unit):

    def perf_decorator(f):

        @functools.wraps(f) #此句如果不加将打印出wrapper为函数名

        def wrapper(*args,**kw):

            t1 = time.time()

            r =f(*args,**kw)

            t2 = time.time()

            t = t2- t1

            if unit!='ms':

                t = t*1000

            print 'call %s in %f %s'%(f.__name__,t,unit)

            return r

        return wrapper

    return perf_decorator

@performance('ms')

def factorial(n):

    return reduce(lambda x,y: x*y, range(1, n+1))

print factorial.__name__

输出：factorial