在抓取网站时，'TypeError：预期的字符串或类似字节的对象'

Question

我正在使用Scrapy和Python抓取一个网站。该代码产生七个意外错误。这是我的代码：

from scrapy import Spider
from scrapy.http import Request
import re
import pymysql
import sys

class EventSpider(Spider):
    name = 'event' #name of the spider
    allowed_domains = ['....com']
    start_urls = ['http://....com/...',
                  'http://....com/....',
                  'http://....com/.....',
                  'http://.....com/.....',
                  'http://www.....com/....',
                  'http://www.....com/....',
                  'http://www....com/.....',
                  'http://www.....com/....',
                  'http://www......com/....',
                  'http://www......com/....',
                  'http://www......com/....',
                  'http://www......com/...',
                  'http://www......com/....',
                  'http://www......com/....',
                  'http://www......com/...',
                  'http://www.....com/.....',
                  'http://www......com/.....']

    def parse(self, response):
        events = response.xpath('//h2/a/@href').extract()
        #events = response.xpath('//a[@class = "event-overly"]').extract()

        for event in events: 
              absolute_url = response.urljoin(event)
              yield Request(absolute_url, callback = self.parse_event)

    def parse_event(self, response):
          title = response.xpath('//title/text()').extract() 
          ''' date = response.xpath('//div/p/text()')[0]. extract()
          start_date = re.search("^[0-9]{1,2}s[A-Z][a-z]{2}(,)s[0-9]{4}",date)
          if(start_date==None):           
             start_date2 =''
          else: 
             start_date2 = start_date.group(0)            
          #end_date = response.xpath('//div/p/text()')[0]. extract()
          end_date = re.search("s[0-9]{1,2}s[A-Z][a-z]{2}(,)s[0-9]{4}", date)
          if(end_date==None):
             end_date2=''
          else:
             end_date2=end_date.group(0)'''   
          #email = response.xpath('//*[@id="more-email-with-dots"]/@value').extract_first()
          #email_final = re.findall("[a-zA-Z0-9_.+-]+@(?!....)[.[a-zA-Z0-9-.]+",email)       
          description = response.xpath('//*[@class = "events-discription-block"]//*/text()').extract()
          description1 = [w.replace('
', '') for w in description]
          description2 = ",".join(description1)
          ''' time = response.xpath('//div/p/text()')[1]. extract() 
          end_time = re.search("s[0-9]{1,2}(:)[0-9]{1,2}(:)[0-9]{1,2}", time)
          if(end_time==None):
              end_time2=''
          else:
              end_time2=end_time.group(0)           
          start_time = re.search("^[0-9]{1,2}(:)[0-9]{1,2}(:)[0-9]{1,2}", time)
          if(start_time==None):
              start_time2=''   
          else:
              start_time2=start_time.group(0) '''
          venue = response.xpath('//*[@id ="more-text-with-dots"]/@value').extract_first()
          pin = re.search("s[0-9]{6}", venue)
          if(pin==None):
            pin2 = ''
          else:
            pin2 = pin.group(0)  
          connection = pymysql.connect (host = "localhost", user = "root", passwd = "Iam90#honest", db = "city_details")
          cursor = connection.cursor ()
          cursor.execute ("select city, state, country from cities_list")
          data = cursor.fetchall ()
          for row in data :
             found = re.search(row[0], venue)
             if(found!=None):
                city = row[0]
                state = row[1]
                country = row[2]
                break                 
             else:
                city = ''
                state = ''
                country = '' 
          creative = response.xpath('//img/@src')[1].extract()        
          yield{
              'title': title,
              #'start_date': start_date2,
              #'end_date': end_date2,
              #'start_time': start_time2,
              #'end_time': end_time2,
              'venue': venue,
              'city': city,
              'state': state,
              'country': country,
              'pin': pin2,
              #'email': email_final,
              'description': description2,
              'creative': creative
          }

这是统计数据：

2018-03-23 19:18:30 [scrapy.statscollectors] INFO: Dumping Scrapy stats:
{'downloader/request_bytes': 45819,
 'downloader/request_count': 109,
 'downloader/request_method_count/GET': 109,
 'downloader/response_bytes': 1024848,
 'downloader/response_count': 109,
 'downloader/response_status_count/200': 90,
 'downloader/response_status_count/301': 19,
 'finish_reason': 'finished',
 'finish_time': datetime.datetime(2018, 3, 23, 10, 18, 30, 182504),
 'item_scraped_count': 64,
 'log_count/DEBUG': 174,
 'log_count/ERROR': 7,
 'log_count/INFO': 8,
 'memusage/max': 54501376,
 'memusage/startup': 54501376,
 'request_depth_max': 1,
 'response_received_count': 90,
 'scheduler/dequeued': 105,
 'scheduler/dequeued/memory': 105,
 'scheduler/enqueued': 105,
 'scheduler/enqueued/memory': 105,
 'spider_exceptions/TypeError': 7,
 'start_time': datetime.datetime(2018, 3, 23, 10, 18, 13, 744056)}
2018-03-23 19:18:30 [scrapy.core.engine] INFO: Spider closed (finished)

更具体地说，显示的错误是：TypeError：期望的字符串或类似字节的对象。我无法弄清楚错误。我无法理解它为什么以及在哪里产生预期的字符串或类似字节的对象错误。