Python装饰器

Python的装饰器可以做一些类似Java SpringBoot AOP切面注解的事情。

# 无参数decorator
import time

def performance(f):
    def fn(*args, **kw):
        start = time.time()
        print 'function start'
        r = f(*args, **kw)
        print 'function finish'
        end = time.time()
        print 'call %s() in %fs' % (f.__name__, (end - start))
        return r
    return fn

@performance
def factorial(n):
    print 'factorial'
    return reduce(lambda x,y: x*y, range(1, n+1))

print factorial(10)

输出：
function start
factorial
function finish
call factorial() in 0.005252s
3628800

# 有参数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) * 1000 if unit=='ms' else (t2 - t1)
            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：
call factorial() in 4.901886 ms
3628800