import time
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)

运行结果：

call factorial() in 0.000000s

3628800

请问time.time()和time.clock()的区别？