使用scrapy做爬虫遇到的一些坑：爬虫使用scrapy爬取网页返回403错误大全以及解决方案

今天学习scrapy爬取网络时遇到的一些坑的可能

正常情况：DEBUG: Crawled (200) <GET http://www.techbrood.com/> (referer: None)

错误情况：DEBUG: Crawled (403) <GET http://www.techbrood.com/> (referer: None)

一，网址的错误

一开始看得是scrapy的文档，然后照着文档输出以下代码：

import scrapy

class DmozSpider(scrapy.spiders.Spider):
    name = "dmoz"
    allowed_domains = ["dmoz.org"]
    start_urls = [
        "http://www.dmoz.org/Computers/Programming/Languages/Python/Books/",
        "http://www.dmoz.org/Computers/Programming/Languages/Python/Resources/"
    ]

    def parse(self, response):
        filename = response.url.split("/")[-2]
        with open(filename, 'wb') as f:
            f.write(response.body)

然后出现返回403错误。找了挺久原因，毕竟其他地方没啥问题，只有通过排除法了，最终将注意力放在网址上，于是将网址输入到浏览器上，果然是错误的。两个网址都是错误的。

解决方案：首先检查你的网址没有错误，这是非常关键的一步。当我改过来之后就出现了。

# -*- coding:utf-8 -*-
import scrapy

class DmozSpider(scrapy.spiders.Spider):
    name = "dmoz"
    allowed_domains = ["dmoz.org"]
    start_urls = [
        "https://blog.csdn.net/weixin_41931602/article/details/80199750",
    ]
    def parse(self, response):
        with open("TY.html", "w") as f:
            f.write(response.body)

二.缩进问题

在看黑马程序员的scrapy的公开视频时，照着打代码也一样错误，而且一直都没有出现爬取出来的网页的HTML源代码。

#scrapy genspider itcast "itcast.cn"
# -*- coding: utf-8 -*-
import scrapy
import sys
reload(sys)
sys.setdefaultencoding("utf-8")
from mySpider.items import ItcastItem

class ItcastSpider(scrapy.Spider):
    name = "itcast"
    allowed_domains = ["itcast.cn"]
    start_urls = ("http://www.itcast.cn/channel/teacher.shtml#ajavaee")

#一定要记得将parse函数缩进
def parse(self, response):
    with open("teacher.html", "w") as f:
        f.write(response.text)
    print response.text

反反复复看好像也没啥问题吧？这次网址也正确啊！检查了许久，才发现我竟然把parse函数写到外面了，难怪没有写出相关的网页代码出来，毕竟我写的代码运行时是没有调用这个函数的。

顺便提一提，parse(self, response) ：解析的方法，每个初始URL完成下载后将被调用，调用的时候传入从每一个URL传回的Response对象来作为唯一参数，主要作用如下：

1. 负责解析返回的网页数据(response.body)，提取结构化数据(生成item)
2. 生成需要下一页的URL请求。

解决方法：一定要记得将parse函数缩进

三.网页有反爬虫

凡是使用爬虫去爬取数据时，都应提前想想爬取的网站上有没有反爬虫，你写的代码都应该有代理吧？

解决方案：在settings文件中添加

USER_AGENT = 'Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/55.0.2883.87 Safari/537.36'

附录：常见的user_agent：

USER_AGENTS = [
    "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; AcooBrowser; .NET CLR 1.1.4322; .NET CLR 2.0.50727)",
    "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0; Acoo Browser; SLCC1; .NET CLR 2.0.50727; Media Center PC 5.0; .NET CLR 3.0.04506)",
    "Mozilla/4.0 (compatible; MSIE 7.0; AOL 9.5; AOLBuild 4337.35; Windows NT 5.1; .NET CLR 1.1.4322; .NET CLR 2.0.50727)",
    "Mozilla/5.0 (Windows; U; MSIE 9.0; Windows NT 9.0; en-US)",
    "Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Win64; x64; Trident/5.0; .NET CLR 3.5.30729; .NET CLR 3.0.30729; .NET CLR 2.0.50727; Media Center PC 6.0)",
    "Mozilla/5.0 (compatible; MSIE 8.0; Windows NT 6.0; Trident/4.0; WOW64; Trident/4.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; .NET CLR 1.0.3705; .NET CLR 1.1.4322)",
    "Mozilla/4.0 (compatible; MSIE 7.0b; Windows NT 5.2; .NET CLR 1.1.4322; .NET CLR 2.0.50727; InfoPath.2; .NET CLR 3.0.04506.30)",
    "Mozilla/5.0 (Windows; U; Windows NT 5.1; zh-CN) AppleWebKit/523.15 (KHTML, like Gecko, Safari/419.3) Arora/0.3 (Change: 287 c9dfb30)",
    "Mozilla/5.0 (X11; U; Linux; en-US) AppleWebKit/527+ (KHTML, like Gecko, Safari/419.3) Arora/0.6",
    "Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.2pre) Gecko/20070215 K-Ninja/2.1.1",
    "Mozilla/5.0 (Windows; U; Windows NT 5.1; zh-CN; rv:1.9) Gecko/20080705 Firefox/3.0 Kapiko/3.0",
    "Mozilla/5.0 (X11; Linux i686; U;) Gecko/20070322 Kazehakase/0.4.5",
    "Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.0.8) Gecko Fedora/1.9.0.8-1.fc10 Kazehakase/0.5.6",
    "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/535.11 (KHTML, like Gecko) Chrome/17.0.963.56 Safari/535.11",
    "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_7_3) AppleWebKit/535.20 (KHTML, like Gecko) Chrome/19.0.1036.7 Safari/535.20",
    "Opera/9.80 (Macintosh; Intel Mac OS X 10.6.8; U; fr) Presto/2.9.168 Version/11.52",
]

如果还不能解决的话，还需要设置以下的

1.添加IP代理：

PROXIES = [
    {'ip_port': '111.11.228.75:80', 'user_pass': ''},
    {'ip_port': '120.198.243.22:80', 'user_pass': ''},
    {'ip_port': '111.8.60.9:8123', 'user_pass': ''},
    {'ip_port': '101.71.27.120:80', 'user_pass': ''},
    {'ip_port': '122.96.59.104:80', 'user_pass': ''},
    {'ip_port': '122.224.249.122:8088', 'user_pass': ''},
]

2.改机器人协议以及cookie

ROBOTSTXT_OBEY = False

COOKIES_ENABLED = False

3.设置延迟   

DOWNLOAD_DELAY = 3

四.在分段函数中所要爬取的url有反爬虫，例如下图加了显示状态码分辨出来的

    def start_requests(self):
        bash_url = 'http://shoudian.bjx.com.cn/NewsList?id=85'
        last_url = '&page='
        for i in range(1,10):#10
            if i == 1:
                url = bash_url
            else:
                url = bash_url + last_url + str(i)
            print(url)
            print(requests.get(url).status_code)
            if requests.get(url).status_code != 403:
                yield Request(url, self.parse)
                print(url)
            else:
                break

解决方案：在请求的url后面添加头文件如以下，头文件可以从问题三的附录中随机取

    def start_requests(self):
        bash_url = 'http://shoudian.bjx.com.cn/NewsList?id=85'
        last_url = '&page='
        for i in range(1,10):#10
            if i == 1:
                url = bash_url
            else:
                url = bash_url + last_url + str(i)
            url_code = requests.get(url,headers={'User-Agent': 'Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/55.0.2883.87 Safari/537.36'}).status_code
            if url_code != 403:
                yield Request(url, self.parse,headers={'User-Agent':'Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/55.0.2883.87 Safari/537.36'})
            else:
                break