Python Twisted框架的HttpClient能够使用代理吗？

Question

我需要通过以下方式访问一个网页

twisted.web.client.getPage()

或者用类似的方法从一个已知地址（比如：www.google.com）下载网页，但我遇到了问题：我在一个代理服务器后面，找不到关于如何配置twisted或工厂使用我的代理的说明，有什么想法吗？

请记住，我需要指定用户名、密码、主机和端口。在我的Linux机器上，我设置了 http_proxy 和 https_proxy 为 http://user:pwd@ip:port

提前谢谢你。

Answer 1

我需要做一些类似的事情，使用基本的身份验证，因为这里的身份验证请求示例代码没有用，所以我写了一个可以用的版本：

import base64

from twisted.internet import defer, reactor
from twisted.web import client, error, http

from ubuntuone.devtools.testcases.squid import SquidTestCase

# ignore common twisted lint errors
# pylint: disable=C0103, W0212


class ProxyClientFactory(client.HTTPClientFactory):
    """Factory that supports proxy."""

    def __init__(self, proxy_url, proxy_port, url, headers=None):
        self.proxy_url = proxy_url
        self.proxy_port = proxy_port
        client.HTTPClientFactory.__init__(self, url, headers=headers)

    def setURL(self, url):
        self.host = self.proxy_url
        self.port = self.proxy_port
        self.url = url
        self.path = url


class ProxyWebClient(object):
    """Provide useful web methods with proxy."""

    def __init__(self, proxy_url=None, proxy_port=None, username=None,
            password=None):
        """Create a new instance with the proxy settings."""
        self.proxy_url = proxy_url
        self.proxy_port = proxy_port
        self.username = username
        self.password = password

    def _process_auth_error(self, failure, url, contextFactory):
        """Process an auth failure."""
        # we try to get the page using the basic auth
        failure.trap(error.Error)
        if failure.value.status == str(http.PROXY_AUTH_REQUIRED):
            auth = base64.b64encode('%s:%s' % (self.username, self.password))
            auth_header = 'Basic ' + auth.strip()
            factory = ProxyClientFactory(self.proxy_url, self.proxy_port, url,
                    headers={'Proxy-Authorization': auth_header})
            # pylint: disable=E1101
            reactor.connectTCP(self.proxy_url, self.proxy_port, factory)
            # pylint: enable=E1101
            return factory.deferred
        else:
            return failure

    def get_page(self, url, contextFactory=None, *args, **kwargs):
        """Download a webpage as a string.

        This method relies on the twisted.web.client.getPage but adds and extra
        step. If there is an auth error the method will perform a second try
        so that the username and password are used.
        """
        scheme, _, _, _ = client._parse(url)
        factory = ProxyClientFactory(self.proxy_url, self.proxy_port, url)
        if scheme == 'https':
            from twisted.internet import ssl
            if contextFactory is None:
                contextFactory = ssl.ClientContextFactory()
            # pylint: disable=E1101
            reactor.connectSSL(self.proxy_url, self.proxy_port,
                               factory, contextFactory)
            # pylint: enable=E1101
        else:
            # pylint: disable=E1101
            reactor.connectTCP(self.proxy_url, self.proxy_port, factory)
            # pylint: enable=E1101
        factory.deferred.addErrback(self._process_auth_error, url,
                                    contextFactory)
        return factory.deferred

Answer 2

要让nosklo的解决方案正常工作，你需要为'401'错误创建一个新的处理程序，这个错误表示需要进行身份验证。可以尝试这样做：

def checkAuthError(self,failure,url):
    failure.trap(error.Error)
    if failure.value.status == '401':
        username = raw_input("User name: ")
        password = getpass.getpass("Password: ")
        auth = base64.encodestring("%s:%s" %(username, password))
        header = "Basic " + auth.strip()
        return client.getPage(
            url, headers={"Authorization": header})
    else:
        return failure

这样做会提示操作员在命令行中输入信息，或者你也可以选择其他方式提供用户名和密码。确保这个处理程序是第一个添加的错误回调，其他处理程序（包括回调）之前都要先添加这个。这还需要导入一些额外的库，比如'base64'、'getpass'和'error'，以便处理命令行的提示。

Answer 3

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

def processResult(page):
    print "I got some data", repr(page)
    reactor.callLater(0.1, reactor.stop)
def dealWithError(err):
    print err.getErrorMessage()
    reactor.callLater(0.1, reactor.stop)

class ProxyClientFactory(client.HTTPClientFactory):
    def setURL(self, url):
        client.HTTPClientFactory.setURL(self, url)
        self.path = url

factory = ProxyClientFactory('http://url_you_want')
factory.deferred.addCallbacks(processResult, dealWithError)

reactor.connectTCP('proxy_address', 3142, factory)
reactor.run()

当然可以！请把你想要翻译的内容发给我，我会帮你用简单易懂的语言解释清楚。