爬虫------爬取百度新闻

首先分析

打开网站之后，然后打开源码，我们发现前面一些新闻标题在源码中可以找到，而下面的标题在源码中找不到

此时我们需要使用fildder抓包来分析这些新闻的网址等信息隐藏在那个地方

这些都有我们要找的信息

我们将网址拷贝出来，在浏览器中打开发现并不是我们要找的源码信息

 

这个url拷贝出来就能发现我们的源码对比一下两个网址的区别

http://news.baidu.com/widget?id=LocalNews&ajax=json&t=1546770768387

http://news.baidu.com/widget?id=civilnews&t=1546770859382 

t表示的只是一个时间戳,我们将第二个网址改成

http://news.baidu.com/widget?id=civilnews&ajax=json

通过上面的网址我们就可以访问到源码

我们受到启发下面的蓝色的网址都只有通过上面的url拼接才能得到我们的源码

1、首先定义我们要爬取的字段有哪些这个在items定义

import scrapy
class BaidunewsItem(scrapy.Item):
    # define the fields for your item here like:
    # name = scrapy.Field()
    # pass
    """1定义爬取的东西"""
    title=scrapy.Field()
    link=scrapy.Field()
    content=scrapy.Field()

2、编写爬虫文件 

# -*- coding: utf-8 -*-
import scrapy
from baidunews.items import BaidunewsItem
from scrapy.http import Request
import re


class NewsSpider(scrapy.Spider):
    name = 'news'
    allowed_domains = ['news.baidu.com']
    start_urls = ['http://news.baidu.com/widget?id=LocalNews&ajax=json']
    all_id = ['LocalNews', 'civilnews', 'InternationalNews', 'EnterNews', 'SportNews', 'FinanceNews', 'TechNews',
              'MilitaryNews', 'InternetNews', 'DiscoveryNews', 'LadyNews', 'HealthNews', 'PicWall']
    all_url = []
    for i in range(len(all_id)):
        current_id = all_id[i]
        current_url = 'http://news.baidu.com/widget?id=' + current_id + '&ajax=json'
        all_url.append(current_url)
    """得到某个栏目块的url"""
    def parse(self, response):
        for i in range(0, len(self.all_url)):
            print("第" + str(i) + "个栏目")
            yield Request(self.all_url[i], callback=self.next)

    """某个模块下面的所有的新闻的url"""
    def next(self, response):
        data = response.body.decode('utf-8', 'ignore')
        # print(self.all_url)
        partten1 = '"url":"(.*?)"'
        partten2 = '"m_url":"(.*?)"'
        url1 = re.compile(partten1, re.S).findall(data)
        url2 = re.compile(partten2, re.S).findall(data)
        if (len(url1) != 0):
            url = url1
        else:
            url = url2
        # print(url)
        # print("===========================")
        for i in range(0, len(url)):
            thisurl = re.sub(r"\\\/", '/', url[i])
            # print(thisurl)
            yield Request(thisurl, callback=self.next2,dont_filter=True)  # thisurl是返回的值，回调函数调next2去处理,

    def next2(self, response):
        item = BaidunewsItem()
        item['link'] = response.url
        item['title'] = response.xpath("/html/head/title/text()").extract()
        item['content'] = response.body
        yield item

下面有几点需要总结的

1、代码中yield Request()中的第一个参数是yield生成器返回的值，第二个callback=XXX是接下来调用那个参数

2、yield Request(thisurl, callback=self.next2,dont_filter=True)  中不添加dont_filter=True是无法获取到我们返回的item的

3教我的大佬解释是allowed_domains = ['news.baidu.com'] 我们中的这个参数设置了网址里面包含这个才能获取到我们要得到信息，例如 current_url = 'http://news.baidu.com/widget?id=' + current_id + '&ajax=json' 而我们每个栏目块下面的单个新闻的并没有news.baidu.com ，只有添加上面dont_filter=True这个参数才能返回我们的item信息

3、我们可以编写pipelines来查看一些返回的item

# -*- coding: utf-8 -*-

# Define your item pipelines here
#
# Don't forget to add your pipeline to the ITEM_PIPELINES setting
# See: https://doc.scrapy.org/en/latest/topics/item-pipeline.html


class BaidunewsPipeline(object):
    def process_item(self, item, spider):
        # print("===========================")
        print(item["title"].decode('utf-8')+item['link']+item['content'])
        return item

4要执行代码之前我们还要在settings中注册

 

# -*- coding: utf-8 -*-

# Scrapy settings for baidunews project
#
# For simplicity, this file contains only settings considered important or
# commonly used. You can find more settings consulting the documentation:
#
#     https://doc.scrapy.org/en/latest/topics/settings.html
#     https://doc.scrapy.org/en/latest/topics/downloader-middleware.html
#     https://doc.scrapy.org/en/latest/topics/spider-middleware.html

BOT_NAME = 'baidunews'

SPIDER_MODULES = ['baidunews.spiders']
NEWSPIDER_MODULE = 'baidunews.spiders'


# Crawl responsibly by identifying yourself (and your website) on the user-agent
#USER_AGENT = 'baidunews (+http://www.yourdomain.com)'

# Obey robots.txt rules
ROBOTSTXT_OBEY = False

# 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 = 3
# 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

# Disable Telnet Console (enabled by default)
#TELNETCONSOLE_ENABLED = False

# Override the default request headers:
#DEFAULT_REQUEST_HEADERS = {
#   'Accept': 'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8',
#   'Accept-Language': 'en',
#}

# Enable or disable spider middlewares
# See https://doc.scrapy.org/en/latest/topics/spider-middleware.html
#SPIDER_MIDDLEWARES = {
#    'baidunews.middlewares.BaidunewsSpiderMiddleware': 543,
#}

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

# Enable or disable extensions
# See https://doc.scrapy.org/en/latest/topics/extensions.html
#EXTENSIONS = {
#    'scrapy.extensions.telnet.TelnetConsole': None,
#}

# Configure item pipelines
# See https://doc.scrapy.org/en/latest/topics/item-pipeline.html


#注册pipeline
ITEM_PIPELINES = {
   'baidunews.pipelines.BaidunewsPipeline': 300,
}

# Enable and configure the AutoThrottle extension (disabled by default)
# See https://doc.scrapy.org/en/latest/topics/autothrottle.html
#AUTOTHROTTLE_ENABLED = True
# The initial download delay
#AUTOTHROTTLE_START_DELAY = 5
# The maximum download delay to be set in case of high latencies
#AUTOTHROTTLE_MAX_DELAY = 60
# The average number of requests Scrapy should be sending in parallel to
# each remote server
#AUTOTHROTTLE_TARGET_CONCURRENCY = 1.0
# Enable showing throttling stats for every response received:
#AUTOTHROTTLE_DEBUG = False

# Enable and configure HTTP caching (disabled by default)
# See https://doc.scrapy.org/en/latest/topics/downloader-middleware.html#httpcache-middleware-settings
#HTTPCACHE_ENABLED = True
#HTTPCACHE_EXPIRATION_SECS = 0
#HTTPCACHE_DIR = 'httpcache'
#HTTPCACHE_IGNORE_HTTP_CODES = []
#HTTPCACHE_STORAGE = 'scrapy.extensions.httpcache.FilesystemCacheStorage'

5然后我们在命令行窗口执行scrapy crawl news就能执行成功

6下面是我们的目录结构