Python中装饰器学习总结

本文研究的主要内容是Python中装饰器相关学习总结，具体如下。

装饰器(decorator)功能

装饰器示例

例1:无参数的函数

from time import ctime, sleepdef timefun(func): def wrappedfunc():  print("%s called at %s"%(func.__name__, ctime()))  func() return wrappedfunc@timefundef foo(): print("I am foo")foo()sleep(2)foo()

分析如下：

上面代码理解装饰器执行行为可理解成

foo = timefun(foo)


1，foo先作为参数赋值给func后,foo接收指向timefun返回的wrappedfunc
2，调用foo(),即等价调用wrappedfunc()
3，内部函数wrappedfunc被引用，所以外部函数的func变量(自由变量)并没有释放
4，func里保存的是原foo函数对象

例2:被装饰的函数有参数

from time import ctime, sleepdef timefun(func): def wrappedfunc(a, b):  print("%s called at %s"%(func.__name__, ctime()))  print(a, b)  func(a, b) return wrappedfunc@timefundef foo(a, b): print(a+b)foo(3,5)sleep(2)foo(2,4)

例3:被装饰的函数有不定长参数

from time import ctime, sleepdef timefun(func): def wrappedfunc(*args, **kwargs):  print("%s called at %s"%(func.__name__, ctime()))  func(*args, **kwargs) return wrappedfunc@timefundef foo(a, b, c): print(a+b+c)foo(3,5,7)sleep(2)foo(2,4,9)

例4:装饰器中的return

from time import ctime, sleepdef timefun(func): def wrappedfunc():  print("%s called at %s"%(func.__name__, ctime()))  func() return wrappedfunc@timefundef foo(): print("I am foo")@timefundef getInfo(): return '----hahah---'foo()sleep(2)foo()print(getInfo())

执行结果:

foo called at Sun Jun 18 00:31:53 2017
I am foo
foo called at Sun Jun 18 00:31:55 2017
I am foo
getInfo called at Sun Jun 18 00:31:55 2017
None

如果修改装饰器为return func()，则运行结果：

foo called at Sun Jun 18 00:34:12 2017
I am foo
foo called at Sun Jun 18 00:34:14 2017
I am foo
getInfo called at Sun Jun 18 00:34:14 2017
----hahah---

小结：一般情况下为了让装饰器更通用，可以有return

例5:装饰器带参数,在原有装饰器的基础上，设置外部变量

from time import ctime, sleepdef 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("itcast")def foo(): print("I am foo")@timefun_arg("python")def too(): print("I am too")foo()sleep(2)foo()too()sleep(2)too()可以理解为foo()==timefun_arg("itcast")(foo)()