新手求教python3如何把dict循环写入csv文件（在进行爬虫时遇到的问题）？

问题描述

爬虫生成dict后，想将其写入csv文件，却出错使用jupyter notebook,window环境。

具体代码如下

import requestsfrom multiprocessing.dummy import Pool as ThreadPoolfrom lxml import etreeimport sysimport timeimport randomimport csvdef spider(url): header={’Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87 Safari/537.36’ } timeout=random.choice(range(31,50)) html = requests.get(url,header,timeout=timeout) time.sleep(random.choice(range(8,16))) selector = etree.HTML(html.text) content_field = selector.xpath(’//*[@class='inner']/p[3]/p[2]/ul/li’) item ={} for each in content_field:g = each.xpath(’a/p[1]/p[1]/h3/span/text()’)go = each.xpath(’a/p[1]/p[2]/p/h3/text()’)h = each.xpath(’a/p[1]/p[2]/p/p/text()[1]’)j= each.xpath(’a/p[1]/p[1]/p/text()[2]’)ge = each.xpath(’a/p[1]/p[2]/p/p/text()[3]’)x = each.xpath(’a/p[1]/p[1]/p/text()[3]’)city = each.xpath(’a/p[1]/p[1]/p/text()[1]’)gg = each.xpath(’a/p[2]/span/text()’)item[’city’]=''.join(city)item[’hangye’]=''.join(hangye)item[’guimo’]=''.join(guimo)item[’gongsi’]=''.join(gongsi)item[’gongzi’]=''.join(gongzi)item[’jingyan’]=''.join(jingyan)item[’xueli’]=''.join(xueli)item[’gongzuoneirong’]=''.join(gongzuoneirong)fieldnames =[’city’,’hangye’,’guimo’,’gongsi’,’gongzi’,’jingyan’,’xueli’,’gongzuoneirong’]with open(’bj.csv’,’a’,newline=’’,errors=’ignore’)as f: f_csv=csv.DictWriter(f,fieldnames=fieldnames) f_csv.writeheader() f_csv.writerow(item)if __name__ == ’__main__’: pool = ThreadPool(4) f=open(’bj.csv’,’w’) page = [] for i in range(1,100):newpage = ’https://www.zhipin.com/c101010100/h_101010100/?query=%E6%95%B0%E6%8D%AE%E8%BF%90%E8%90%A5&page=’+str(i) + ’&ka=page-’ + str(i)page.append(newpage) results = pool.map(spider,page) pool.close() pool.join() f.close()

运行上面代码，提示错误为

ValueError: too many values to unpack (expected 2)通过查询原因是要将dict遍历，需要dict.items()的形式。但在上述代码中如何实现，一直没有理顺，求教各位

问题解答

不好意思哈，现在才有时间来回答你的问题，看到你根据我的建议把代码改过来了，下面我把改过的代码贴出来，我运行过，是没问题的

import requestsfrom multiprocessing.dummy import Poolfrom lxml import etreeimport timeimport randomimport csvdef spider(url): header = {’User-Agent’: ’Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87 Safari/537.36’ } timeout = random.choice(range(31, 50)) html = requests.get(url, headers=header, timeout=timeout) time.sleep(random.choice(range(8, 16))) selector = etree.HTML(html.text) content_field = selector.xpath(’//*[@class='inner']/p[3]/p[2]/ul/li’) item = {} for each in content_field:g = each.xpath(’a/p[1]/p[1]/h3/span/text()’)go = each.xpath(’a/p[1]/p[2]/p/h3/text()’)h = each.xpath(’a/p[1]/p[2]/p/p/text()[1]’)j = each.xpath(’a/p[1]/p[1]/p/text()[2]’)ge = each.xpath(’a/p[1]/p[2]/p/p/text()[3]’)x = each.xpath(’a/p[1]/p[1]/p/text()[3]’)city = each.xpath(’a/p[1]/p[1]/p/text()[1]’)gg = each.xpath(’a/p[2]/span/text()’)item[’city’] = ''.join(city)item[’hangye’] = ''.join(g)item[’guimo’] = ''.join(go)item[’gongsi’] = ''.join(h)item[’gongzi’] = ''.join(j)item[’jingyan’] = ''.join(ge)item[’xueli’] = ''.join(x)item[’gongzuoneirong’] = ''.join(gg)fieldnames = [’city’, ’hangye’, ’guimo’, ’gongsi’, ’gongzi’, ’jingyan’, ’xueli’, ’gongzuoneirong’]with open(’bj.csv’, ’a’, newline=’’, errors=’ignore’)as f: f_csv = csv.DictWriter(f, fieldnames=fieldnames) f_csv.writeheader() f_csv.writerow(item)if __name__ == ’__main__’: f = open(’bj.csv’, ’w’) page = [] for i in range(1, 100):newpage = ’https://www.zhipin.com/c101010100/h_101010100/?query=%E6%95%B0%E6%8D%AE%E8%BF%90%E8%90%A5&page=’ + str( i) + ’&ka=page-’ + str(i)page.append(newpage) print(page) pool = Pool(4) results = pool.map(spider, page) pool.close() pool.join() f.close()

这里主要是header,你原来是set类型，我修改后是dict类型

这里还需要给你一些建议

你的代码是放到ide还是文本编辑器中运行的？有的东西在ide下明显会报错啊

建议新手从开始学的时候就遵守PEP8规范，别养成了坏习惯，你看看你的命名

item = {’a’:1, ’b’:2}fieldnames = [’a’, ’b’]with open(’test.csv’, ’a’) as f: f_csv = DictWriter(f, fieldnames=fieldnames) f_csv.writeheader() f_csv.writerow(item)

我这样写并没报错喔

writerow就是直接接收dict的吧，你这个问题，我感觉是因为item的key与你表头不对应

因为在 fields 中指定的某些列名在 item 中不存在