Scrapy爬虫脚本无输出但Shell中可正常运行问题求助

问题描述 #

爬取www.1mg.com药品信息时，执行Scrapy爬虫脚本无任何数据输出，但在Scrapy Shell中运行相同CSS选择器能正常获取目标数据。

爬虫代码 #

import scrapy

class MedspiderSpider(scrapy.Spider):
    name = "medspider"
    allowed_domains = ["www.1mg.com"]
    start_urls = ["https://www.1mg.com/drugs-all-medicines"]

    def parse(self, response):
        meds = response.css('div.style__flex-1___A_qoj')
        
        for med in meds:
            yield{
                'name' : med.css('div div::text').get(),
                'price' : med.css('div:has(> span)::text').getall()[-1],
                'strip content' :  med.css('div::text').getall()[-4],
                'manufacturer' :  med.css('div::text').getall()[-3]
            }

运行日志 #

2023-05-28 11:44:22 [scrapy.utils.log] INFO: Scrapy 2.9.0 started (bot: tata1mg)
2023-05-28 11:44:22 [scrapy.utils.log] INFO: Versions: lxml 4.9.2.0, libxml2 2.9.12, cssselect 1.2.0, parsel 1.8.1, w3lib 2.1.1, Twisted 22.10.0, Python 3.11.0 (main, Oct 24 2022, 18:26:48) [MSC v.1933 64 bit (AMD64)], pyOpenSSL 23.1.1 (OpenSSL 3.1.0 14 Mar 2023), cryptography 40.0.2, Platform Windows-10-10.0.22624-SP0
2023-05-28 11:44:22 [scrapy.crawler] INFO: Overridden settings:
{'BOT_NAME': 'tata1mg',
 'FEED_EXPORT_ENCODING': 'utf-8',
 'NEWSPIDER_MODULE': 'tata1mg.spiders',
 'REQUEST_FINGERPRINTER_IMPLEMENTATION': '2.7',
 'ROBOTSTXT_OBEY': True,
 'SPIDER_MODULES': ['tata1mg.spiders'],
 'TWISTED_REACTOR': 'twisted.internet.asyncioreactor.AsyncioSelectorReactor'}
2023-05-28 11:44:22 [asyncio] DEBUG: Using selector: SelectSelector
2023-05-28 11:44:22 [scrapy.utils.log] DEBUG: Using reactor: twisted.internet.asyncioreactor.AsyncioSelectorReactor
2023-05-28 11:44:22 [scrapy.utils.log] DEBUG: Using asyncio event loop: asyncio.windows_events._WindowsSelectorEventLoop
2023-05-28 11:44:22 [scrapy.extensions.telnet] INFO: Telnet Password: 74ffa37a1d23bc25
2023-05-28 11:44:22 [scrapy.middleware] INFO: Enabled extensions:
['scrapy.extensions.corestats.CoreStats',
 'scrapy.extensions.telnet.TelnetConsole',
 'scrapy.extensions.logstats.LogStats']
2023-05-28 11:44:22 [scrapy.middleware] INFO: Enabled downloader middlewares:
['scrapy.downloadermiddlewares.robotstxt.RobotsTxtMiddleware',
 'scrapy.downloadermiddlewares.httpauth.HttpAuthMiddleware',
 'scrapy.downloadermiddlewares.downloadtimeout.DownloadTimeoutMiddleware',
 'scrapy.downloadermiddlewares.defaultheaders.DefaultHeadersMiddleware',
 'scrapy.downloadermiddlewares.useragent.UserAgentMiddleware',
 'scrapy.downloadermiddlewares.retry.RetryMiddleware',
 'scrapy.downloadermiddlewares.redirect.MetaRefreshMiddleware',
 'scrapy.downloadermiddlewares.httpcompression.HttpCompressionMiddleware',
 'scrapy.downloadermiddlewares.redirect.RedirectMiddleware',
 'scrapy.downloadermiddlewares.cookies.CookiesMiddleware',
 'scrapy.downloadermiddlewares.httpproxy.HttpProxyMiddleware',
 'scrapy.downloadermiddlewares.stats.DownloaderStats']
2023-05-28 11:44:22 [scrapy.middleware] INFO: Enabled spider middlewares:
['scrapy.spidermiddlewares.httperror.HttpErrorMiddleware',
 'scrapy.spidermiddlewares.offsite.OffsiteMiddleware',
 'scrapy.spidermiddlewares.referer.RefererMiddleware',
 'scrapy.spidermiddlewares.urllength.UrlLengthMiddleware',
 'scrapy.spidermiddlewares.depth.DepthMiddleware']
2023-05-28 11:44:22 [scrapy.middleware] INFO: Enabled item pipelines:
[]
2023-05-28 11:44:22 [scrapy.core.engine] INFO: Spider opened
2023-05-28 11:44:23 [scrapy.extensions.logstats] INFO: Crawled 0 pages (at 0 pages/min), scraped 0 items (at 0 items/min)
2023-05-28 11:44:23 [scrapy.extensions.telnet] INFO: Telnet console listening on 127.0.0.1:6023
2023-05-28 11:44:23 [scrapy.core.engine] DEBUG: Crawled (200) <GET https://www.1mg.com/robots.txt> (referer: None)
2023-05-28 11:44:23 [scrapy.core.engine] DEBUG: Crawled (200) <GET https://www.1mg.com/drugs-all-medicines> (referer: None)
2023-05-28 11:44:23 [scrapy.core.engine] INFO: Closing spider (finished)
2023-05-28 11:44:23 [scrapy.statscollectors] INFO: Dumping Scrapy stats:
{'downloader/request_bytes': 896,
 'downloader/request_count': 2,
 'downloader/request_method_count/GET': 2,
 'downloader/response_bytes': 48250,
 'downloader/response_count': 2,
 'downloader/response_status_count/200': 2,
 'elapsed_time_seconds': 0.670526,
 'finish_reason': 'finished',
 'finish_time': datetime.datetime(2023, 5, 28, 6, 14, 23, 763883),
 'httpcompression/response_bytes': 264903,
 'httpcompression/response_count': 2,
 'log_count/DEBUG': 5,
 'log_count/INFO': 10,
 'response_received_count': 2,
 'robotstxt/request_count': 1,
 'robotstxt/response_count': 1,
 'robotstxt/response_status_count/200': 1,
 'scheduler/dequeued': 1,
 'scheduler/dequeued/memory': 1,
 'scheduler/enqueued': 1,
 'scheduler/enqueued/memory': 1,
 'start_time': datetime.datetime(2023, 5, 28, 6, 14, 23, 93357)}
2023-05-28 11:44:23 [scrapy.core.engine] INFO: Spider closed (finished)

Scrapy Shell测试结果 #

In [21]: med.css('div div div ::text').get()
Out[21]: 'Augmentin 625 Duo Tablet'

In [25]: med.css('div::text').getall()[-4]
Out[25]: 'strip of 10 tablets'

In [26]: med.css('div::text').getall()[-3]
Out[26]: 'Glaxo SmithKline Pharmaceuticals Ltd'

问题原因分析 #

1. 动态类名失效：你使用的style__flex-1___A_qoj是网站动态生成的哈希类名，这类名称会随网站更新或请求头变化而改变，导致爬虫请求的页面中找不到对应元素。
2. User-Agent被识别：Scrapy默认的User-Agent格式为Scrapy/版本号，容易被反爬机制识别并返回简化页面；而Scrapy Shell默认使用接近浏览器的User-Agent，能获取完整内容。
3. Robots协议限制：虽然页面返回200状态码，但网站robots.txt可能存在隐性限制，导致爬虫无法获取完整数据。

解决方案 #

1. 替换为稳定选择器 #

放弃依赖动态类名，改用基于页面结构或固定属性的选择器，示例如下：

def parse(self, response):
    # 用XPath定位药品卡片容器，依赖固定类名片段
    meds = response.xpath('//div[contains(@class, "style__product-card")]')
    for med in meds:
        yield {
            'name': med.xpath('.//h3/text()').get(),
            'price': med.xpath('.//div[contains(@class, "style__price-tag")]/text()').get(),
            'strip_content': med.xpath('.//div[contains(@class, "style__pack-size")]/text()').get(),
            'manufacturer': med.xpath('.//div[contains(@class, "style__manufacturer")]/text()').get()
        }

2. 设置浏览器级User-Agent #

在项目settings.py中添加真实浏览器的User-Agent：

USER_AGENT = 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/114.0.0.0 Safari/537.36'

3. 临时禁用Robots协议 #

在settings.py中修改配置，跳过Robots检查：

ROBOTSTXT_OBEY = False

4. 验证返回内容 #

在parse函数中添加代码，保存爬虫获取的页面到本地，对比与Shell中内容的差异：

def parse(self, response):
    with open('response.html', 'w', encoding='utf-8') as f:
        f.write(response.text)
    meds = response.css('div.style__flex-1___A_qoj')
    print(f"找到{len(meds)}个药品元素")
    # 后续处理逻辑...

内容的提问来源于stack exchange，提问作者Lucyfer