#! -*- encoding:utf-8 -*-        import base64                    import sys        import random        PY3 = sys.version_info[0] >= 3        def base64ify(bytes_or_str):            if PY3 and isinstance(bytes_or_str, str):                input_bytes = bytes_or_str.encode('utf8')            else:                input_bytes = bytes_or_str            output_bytes = base64.urlsafe_b64encode(input_bytes)            if PY3:                return output_bytes.decode('ascii')            else:                return output_bytes        class ProxyMiddleware(object):                
            def process_request(self, request, spider):                # 代理服务器(产品官网 www.16yun.cn)                proxyHost = "t.16yun.cn"                proxyPort = "31111"                # 代理验证信息                proxyUser = "username"                proxyPass = "password"                request.meta['proxy'] = "http://{0}:{1}".format(proxyHost,proxyPort)                # 添加验证头                encoded_user_pass = base64ify(proxyUser + ":" + proxyPass)                request.headers['Proxy-Authorization'] = 'Basic ' + encoded_user_pass                                    # 设置IP切换头(根据需求)                tunnel = random.randint(1,10000)                request.headers['Proxy-Tunnel'] = str(tunnel)