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<h1 id="python设计模式之装饰器模式"><a href="http://dongweiming.github.io/python-decorator.html"Permalink to python设计模式之装饰器模式"" target="_blank">python设计模式之装饰器模式</a></h1><h2 id="装饰器模式">装饰器模式</h2><p>在python中装饰器已经算是代码级别的模式了，装饰器这个@符号会深入你我心，而这个技能也是写代码必备之大技.增加额外的功能，装饰器其实就是在你执行类或者函数之前给你封装了一层或者多层(多个装饰器，这在web框架代码中很常见)操作，z但是不影响你最后执行代码
其实原理就是：有一些函数或者类里面有一些步骤是一样的(比如对数据缓存，比如加锁和释放)，那么你就可以把这些重复的东西拿出来放在装饰器里面，这样每个函数或者类就不需要写这样多的代码，而抽象出来。而通过这样的额外功能可以还能让你执行的函数或者类计数等</p><h2 id="python的例子">python的例子</h2><p>一时间还想不起来干啥，好吧写了个缓存数据到redis的装饰器</p><pre><code>from functools import wraps
from redis import Redis
redis = Redis()
def cached(timeout=5 * 60):
def decorator(f):
# wraps帮你将函数原来的属性复制过来
@wraps(f)
def decorated_function(*args, **kwargs):
# 以执行函数的参数为键
key = str(args)
rv = redis.get(key)
# 发现缓存过直接返回
if rv is not None:
print 'Has match: ', rv
return rv
rv = f(*args, **kwargs)
redis.setex(key, rv, time=timeout)
return rv
return decorated_function
return decorator
@cached()
def printNumber(num):
return num
if __name__ == '__main__':
# 注意列表数据有重复
for i in [1, 2, 5, 11, 2, 7, 9, 1]:
print printNumber(i)</code></pre>
<p>说到装饰器就要提一个模块:
<a href="http://micheles.googlecode.com/hg/decorator/documentation.html" target="_blank">decorator</a> 它是
Michele Simionato 为简化python的decorator的使用难度而开发的，强烈建议深入学习</p>
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