python - 扭曲的 Python getPage

Question

我试图就此获得支持，但我完全感到困惑。

这是我的代码:

from twisted.internet import reactor
from twisted.web.client import getPage
from twisted.web.error import Error
from twisted.internet.defer import DeferredList
from sys import argv

class GrabPage:
 def __init__(self, page):
  self.page = page

 def start(self, *args):
  if args == ():
   # We apparently don't need authentication for this
   d1 = getPage(self.page)
  else:
   if len(args) == 2:
    # We have our login information
    d1 = getPage(self.page, headers={"Authorization": " ".join(args)})
   else:
    raise Exception('Missing parameters')

  d1.addCallback(self.pageCallback)
  dl = DeferredList([d1])
  d1.addErrback(self.errorHandler)
  dl.addCallback(self.listCallback)

 def errorHandler(self,result):
  # Bad thingy!
  pass

 def pageCallback(self, result):
  return result

 def listCallback(self, result):
  print result

a = GrabPage('http://www.google.com')
data = a.start() # Not the HTML

我希望在调用 start() 时获取提供给 pageCallback 的 HTML。这对我来说是一个皮塔饼。泰!为我糟糕的编码感到抱歉。

Answer 1

您缺少 Twisted 运作方式的基础知识。这一切都围绕着 reactor，您甚至从未运行过它。把 react 堆想象成这样:

_{(来源:krondo.com)}

在您启动 react 器之前，通过设置延迟，您所做的只是将它们链接起来，没有可触发的事件。

我建议你给Twisted Intro通过 Dave Peticolas一读。它速度很快，而且确实为您提供了 Twisted 文档没有提供的所有缺失信息。

无论如何，这里是尽可能最基本的getPage用法示例:

from twisted.web.client import getPage
from twisted.internet import reactor

url = 'http://aol.com'

def print_and_stop(output):
    print output
    if reactor.running:
       reactor.stop()

if __name__ == '__main__':
    print 'fetching', url
    d = getPage(url)
    d.addCallback(print_and_stop)
    reactor.run()

由于 getPage 返回一个延迟链，我将回调 print_and_stop 添加到延迟链。之后，我启动了 reactor。 react 器触发 getPage，然后触发 print_and_stop，打印来自 aol.com 的数据，然后停止 react 器。

编辑以显示 OP 代码的工作示例:

class GrabPage:
    def __init__(self, page):
        self.page = page
        ########### I added this:
        self.data = None

    def start(self, *args):
        if args == ():
            # We apparently don't need authentication for this
            d1 = getPage(self.page)
        else:
            if len(args) == 2:
                # We have our login information
                d1 = getPage(self.page, headers={"Authorization": " ".join(args)})
            else:
                raise Exception('Missing parameters')

        d1.addCallback(self.pageCallback)
        dl = DeferredList([d1])
        d1.addErrback(self.errorHandler)
        dl.addCallback(self.listCallback)

    def errorHandler(self,result):
        # Bad thingy!
        pass

    def pageCallback(self, result):
        ########### I added this, to hold the data:
        self.data = result
        return result

    def listCallback(self, result):
        print result
        # Added for effect:
        if reactor.running:
            reactor.stop()

a = GrabPage('http://google.com')
########### Just call it without assigning to data
#data = a.start() # Not the HTML
a.start()

########### I added this:
if not reactor.running:
    reactor.run()

########### Reference the data attribute from the class
data = a.data
print '------REACTOR STOPPED------'
print
########### First 100 characters of a.data:
print '------a.data[:100]------'
print data[:100]