Python爬虫入门教程【19】： B站博人传评论数据抓取 scrapy

1. B站博人传评论数据爬取简介

今天想了半天不知道抓啥，去B站看跳舞的小姐姐，忽然看到了评论，那就抓取一下B站的评论数据，视频动画那么多，也不知道抓取哪个，选了一个博人传跟火影相关的，抓取看看。网址： https://www.bilibili.com/bangumi/media/md5978/?from=search&seid=16013388136765436883#short
在这个网页看到了18560条短评，数据量也不大，抓取看看，使用的还是scrapy。

2. B站博人传评论数据案例—获取链接

从开发者工具中你能轻易的得到如下链接，有链接之后就好办了，如何创建项目就不在啰嗦了，我们直接进入主题。

我在代码中的parse函数中，设定了两个yield一个用来返回items 一个用来返回requests。
然后实现一个新的功能，每次访问切换UA，这个点我们需要使用到中间件技术。


class BorenSpider(scrapy.Spider):BASE_URL = "https://bangumi.bilibili.com/review/web_api/short/list?media_id=5978&folded=0&page_size=20&sort=0&cursor={}"name = 'Boren'allowed_domains = ['bangumi.bilibili.com']start_urls = [BASE_URL.format("76742479839522")]def parse(self, response):print(response.url)resdata = json.loads(response.body_as_unicode())if resdata["code"] == 0:# 获取最后一个数据if len(resdata["result"]["list"]) > 0:data = resdata["result"]["list"]cursor = data[-1]["cursor"]for one in data:item = BorenzhuanItem()item["author"]  = one["author"]["uname"]item["content"] = one["content"]item["ctime"] = one["ctime"]item["disliked"] = one["disliked"]item["liked"] = one["liked"]item["likes"] = one["likes"]item["user_season"] = one["user_season"]["last_ep_index"] if "user_season" in one else ""item["score"] = one["user_rating"]["score"]yield itemyield scrapy.Request(self.BASE_URL.format(cursor),callback=self.parse)
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3. B站博人传评论数据案例—实现随机UA

第一步，在settings文件中添加一些UserAgent,我从互联网找了一些

USER_AGENT_LIST=["Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.1 (KHTML, like Gecko) Chrome/22.0.1207.1 Safari/537.1","Mozilla/5.0 (X11; CrOS i686 2268.111.0) AppleWebKit/536.11 (KHTML, like Gecko) Chrome/20.0.1132.57 Safari/536.11","Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/536.6 (KHTML, like Gecko) Chrome/20.0.1092.0 Safari/536.6","Mozilla/5.0 (Windows NT 6.2) AppleWebKit/536.6 (KHTML, like Gecko) Chrome/20.0.1090.0 Safari/536.6","Mozilla/5.0 (Windows NT 6.2; WOW64) AppleWebKit/537.1 (KHTML, like Gecko) Chrome/19.77.34.5 Safari/537.1","Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/536.5 (KHTML, like Gecko) Chrome/19.0.1084.9 Safari/536.5","Mozilla/5.0 (Windows NT 6.0) AppleWebKit/536.5 (KHTML, like Gecko) Chrome/19.0.1084.36 Safari/536.5","Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/536.3 (KHTML, like Gecko) Chrome/19.0.1063.0 Safari/536.3","Mozilla/5.0 (Windows NT 5.1) AppleWebKit/536.3 (KHTML, like Gecko) Chrome/19.0.1063.0 Safari/536.3","Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; Trident/4.0; SE 2.X MetaSr 1.0; SE 2.X MetaSr 1.0; .NET CLR 2.0.50727; SE 2.X MetaSr 1.0)","Mozilla/5.0 (Windows NT 6.2) AppleWebKit/536.3 (KHTML, like Gecko) Chrome/19.0.1062.0 Safari/536.3","Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/536.3 (KHTML, like Gecko) Chrome/19.0.1062.0 Safari/536.3","Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; 360SE)","Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/536.3 (KHTML, like Gecko) Chrome/19.0.1061.1 Safari/536.3","Mozilla/5.0 (Windows NT 6.1) AppleWebKit/536.3 (KHTML, like Gecko) Chrome/19.0.1061.1 Safari/536.3","Mozilla/5.0 (Windows NT 6.2) AppleWebKit/536.3 (KHTML, like Gecko) Chrome/19.0.1061.0 Safari/536.3","Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/535.24 (KHTML, like Gecko) Chrome/19.0.1055.1 Safari/535.24","Mozilla/5.0 (Windows NT 6.2; WOW64) AppleWebKit/535.24 (KHTML, like Gecko) Chrome/19.0.1055.1 Safari/535.24"
]

第二步，在settings文件中设置 “DOWNLOADER_MIDDLEWARES”

# Enable or disable downloader middlewares
# See https://doc.scrapy.org/en/latest/topics/downloader-middleware.html
DOWNLOADER_MIDDLEWARES = {#'borenzhuan.middlewares.BorenzhuanDownloaderMiddleware': 543,'borenzhuan.middlewares.RandomUserAgentMiddleware': 400,
}

第三步，在 middlewares.py 文件中导入 settings模块中的 USER_AGENT_LIST 方法

from borenzhuan.settings import USER_AGENT_LIST # 导入中间件
import randomclass RandomUserAgentMiddleware(object):def process_request(self, request, spider):rand_use  = random.choice(USER_AGENT_LIST)if rand_use:request.headers.setdefault('User-Agent', rand_use)

好了，随机的UA已经实现，你可以在parse函数中编写如下代码进行测试

print(response.request.headers)

4. B站博人传评论数据----完善item

这个操作相对简单，这些数据就是我们要保存的数据了。！

   author = scrapy.Field()content = scrapy.Field()ctime = scrapy.Field()disliked = scrapy.Field()liked = scrapy.Field()likes = scrapy.Field()score = scrapy.Field()user_season = scrapy.Field()

5. B站博人传评论数据案例—提高爬取速度

在settings.py中设置如下参数：


# Configure maximum concurrent requests performed by Scrapy (default: 16)
CONCURRENT_REQUESTS = 32
# Configure a delay for requests for the same website (default: 0)
# See https://doc.scrapy.org/en/latest/topics/settings.html#download-delay
# See also autothrottle settings and docs
DOWNLOAD_DELAY = 1
# The download delay setting will honor only one of:
CONCURRENT_REQUESTS_PER_DOMAIN = 16
CONCURRENT_REQUESTS_PER_IP = 16
# Disable cookies (enabled by default)
COOKIES_ENABLED = False

解释说明

一、降低下载延迟

DOWNLOAD_DELAY = 0

将下载延迟设为0，这时需要相应的防ban措施，一般使用user agent轮转，构建user agent池，轮流选择其中之一来作为user agent。

二、多线程

CONCURRENT_REQUESTS = 32
CONCURRENT_REQUESTS_PER_DOMAIN = 16
CONCURRENT_REQUESTS_PER_IP = 16

scrapy网络请求是基于Twisted，而Twisted默认支持多线程，而且scrapy默认也是通过多线程请求的，并且支持多核CPU的并发，我们通过一些设置提高scrapy的并发数可以提高爬取速度。

三、禁用cookies

COOKIES_ENABLED = False

6. B站博人传评论数据案例—保存数据

最后在pipelines.py 文件中，编写保存代码即可

import os
import csvclass BorenzhuanPipeline(object):def __init__(self):store_file = os.path.dirname(__file__)+'/spiders/bore.csv'self.file = open(store_file,"a+",newline="",encoding="utf-8")self.writer = csv.writer(self.file)def process_item(self, item, spider):try:self.writer.writerow((item["author"],item["content"],item["ctime"],item["disliked"],item["liked"],item["likes"],item["score"],item["user_season"]))except Exception as e:print(e.args)def close_spider(self, spider):self.file.close()
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运行代码之后，发现过了一会报错了

去看了一眼，原来是数据爬取完毕_！！！