[Python进阶]002.装饰器(1)
装饰器(1)
介绍
- Python的装饰器叫
Decorator，就是对一个模块做装饰。 - 作用: 为已存在的对象添加额外功能。
- 与Java中的注解相似，就是在方法前加@XXX来对这个方法做装饰。
- 与Java中的注解相当复杂不同，Python的装饰器相当简单。
- 函数式编程
- 面向切片编程
HelloWorld
需求
def fun(i):
print i
这是一个简单的方法，现在我们要在执行这个方法前后在执行一些其他代码，比如计算运行时间。
简单的方式就是:
import time def fun(i):
t = time.time()
print i
t = time.time() - t # 计算运行时间
print '运行时间:',str(t) # 打印时间
这种方式不方便，也不能复用。
使用函数式编程
import time # 计算运行时间
def exec_time(fn, i): # fn:方法; i:方法的参数
t = time.time()
fn(i) # 调用fn
t = time.time() - t # 计算运行时间
print '运行时间:',str(t) # 打印时间 def fun(i):
print i # 调用
exec_time(fun, i)
使用这种方式，在实际调用时，需要包裹一层exec_time方法，虽然可以复用，使用起来但也并不灵活。
加入装饰器
下面我们就来加入修饰器
from functools import wraps # 引入装饰器需要的包
import time # 定义一个装饰器
def exec_time(fn): # 参数fn：要修饰的方法，就是我们的fun
@wraps(fn)
def _(i): # 修饰方法，参数i是fun传过来的参数
t = time.time()
fn(i) # 执行方法
t = time.time() - t
print '运行时间:',str(t)
return _ # 返回修饰后方法
这样就完成了一个计算运行时间的装饰器。
@exec_time
def fun(i):
print i @exec_time
def fun2(i):
print 'fun2', i
使用起来十分方便。
解析
- 加入了
@exec_time后的fun方法，在调用时会自动调用相当于exec_time(fun)的方法。 fun方法被exec_time装饰了，方法在开始和结束时会进行计时，并打印花费时间，这就是一个横切面，这种编程方式就是面向切面的编程。在方法执行的过程中横向插入逻辑，在很多地方都能大量减少重复代码。
本站文章为宝宝巴士 SD.Team原创，转载务必在明显处注明：（作者官方网站：宝宝巴士)
转载自【宝宝巴士SuperDo团队】 原文链接: http://www.cnblogs.com/superdo/p/4829345.html
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