源码库

python教程

源码库-建站教程-脚本之家-python教程- 正文

python构建自定义回调函数详解

2017-08-31 源码库 www.aspku.com 大字

回调函数用起来比较爽。特别是在js中,满世界全是回调,那么在python/272742.html">python/265853.html">python中,怎么来优雅地实现自己的回调函数呢

下面贴一个我写的例子

class BaseHandler(object):

  def crawl(self, url, **kwargs):
    if kwargs.get('callback'):
      callback = kwargs['callback']
      if isinstance(callback, basestring) and hasattr(self, callback):
        func = getattr(self, callback)
      elif hasattr(callback, 'im_self') and callback.im_self is self:
        func = callback

    resp = requests.get(url)
    return func(resp)


class Anjuke(BaseHandler):
  def on_start(self):
    self.crawl(start_url, callback=self.index_url)

  def index_url(self, response):
    print response.text

a = Anjuke()
print a.on_start()

其实就是通过kwargs获取到callback的对象/字符串,然后通过getattr(self, callback)来反射得到回调的方法,然后调用即可。

接着可以进一步抽象,增加回调方法的复用,于是BaseHandler可以改写成装饰器方式

def callback(f):
  def wrapper(obj, *args, **kwargs):
    resp = f(obj, *args, **kwargs)
    if kwargs.get('callback'):
      mcallback = kwargs['callback']
      if isinstance(callback, basestring) and hasattr(obj, mcallback):
        func = getattr(obj, mcallback)
      elif hasattr(mcallback, 'im_self') and mcallback.im_self is obj:
        func = mcallback
        kwargs['callback'] = func.__name__
      else:
        raise NotImplementedError("self.%s() not implemented!" % callback)

    return func(resp)
  return wrapper


class BaseHandler(object):

  @callback
  def crawl(self, url, **kwargs):
    url = quote_chinese(_build_url(url.strip(), kwargs.get('params')))
    return requests.get(url)

分享到:

相关阅读

阅读排行

参与评论