Python爬虫错误之twisted.web.error.SchemeNotSupported: Unsupported scheme: b''

在使用scrapy爬虫时，出现了下面了的错误

Traceback (most recent call last):
  File "E:\project\venv\lib\site-packages\twisted\internet\defer.py", line 1416, in _inlineCallbacks
    result = result.throwExceptionIntoGenerator(g)
  File "E:\project\venv\lib\site-packages\twisted\python\failure.py", line 491, in throwExceptionIntoGenerator
    return g.throw(self.type, self.value, self.tb)
  File "E:\project\venv\lib\site-packages\scrapy\core\downloader\middleware.py", line 43, in process_request
    defer.returnValue((yield download_func(request=request,spider=spider)))
  File "E:\project\venv\lib\site-packages\scrapy\utils\defer.py", line 45, in mustbe_deferred
    result = f(*args, **kw)
  File "E:\project\venv\lib\site-packages\scrapy\core\downloader\handlers\__init__.py", line 65, in download_request
    return handler.download_request(request, spider)
  File "E:\project\venv\lib\site-packages\scrapy\core\downloader\handlers\http11.py", line 67, in download_request
    return agent.download_request(request)
  File "E:\project\venv\lib\site-packages\scrapy\core\downloader\handlers\http11.py", line 331, in download_request
    method, to_bytes(url, encoding='ascii'), headers, bodyproducer)
  File "E:\project\venv\lib\site-packages\scrapy\core\downloader\handlers\http11.py", line 252, in request
    proxyEndpoint = self._getEndpoint(self._proxyURI)
  File "E:\project\venv\lib\site-packages\twisted\web\client.py", line 1635, in _getEndpoint
    return self._endpointFactory.endpointForURI(uri)
  File "E:\project\venv\lib\site-packages\twisted\web\client.py", line 1513, in endpointForURI
    raise SchemeNotSupported("Unsupported scheme: %r" % (uri.scheme,))
twisted.web.error.SchemeNotSupported: Unsupported scheme: b''

经调查是在下载中间件中设置代理是出现了错误：

class IpProxyDownloadMiddleware(object):
    PROXIES = ['110.52.235.131:9999','110.52.235.249:9999','112.17.38.141:3128']

    def process_request(self,request,spider):
        proxy = random.choice(self.PROXIES)
        request.meta['proxy'] = proxy

在上面的下载中间件中设置代理时，需要添加协议名称，“http://”或者“https://”。

如下：

class IpProxyDownloadMiddleware(object):
    PROXIES = ['110.52.235.131:9999','110.52.235.249:9999','112.17.38.141:3128']

    def process_request(self,request,spider):
        proxy = random.choice(self.PROXIES)
        request.meta['proxy'] = 'http://'+proxy

问题成功解决。

Python爬虫错误之twisted.web.error.SchemeNotSupported: Unsupported scheme: b''

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