1       Scrapy设置User-Agent

1.1   在settings.py文件中设置USER_AGENT参数即可实现

1.1.1  使用固定User-Agent方法

在settings.py文件中加入如下代码即可（USER_AGENT是固定写法），具体使用什么agent可以自己更改下面蓝色字体内容。

USER_AGENT = '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)

1.1.2  使用随机User-Agent方法

在settings.py文件中通过创建一个agent列表，然后通过从中随机取出1个赋值给USER_AGENT变量即可

代码如下：

import random

UserAgentList = [

    "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)",

    ]

USER_AGENT = random.choice(UserAgentList)

1.1.3  使用第三方user-agent库（fake-useragent）实现设置agent方法

在settings.py文件中加入如下代码：

from fake_useragent import UserAgent

ua = UserAgent()

USER_AGENT = ua.random

1.2   通过写middleware方法实现

1.2.1  通过在setting文件中自己编写user-agent方法

在setting.py文件中写一个UserAgentList列表

UserAgentList = [
    'Mozilla/5.0 (Windows NT 6.2; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/27.0.1500.55 Safari/537.36',
    'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_8_2) AppleWebKit/537.17 (KHTML, like Gecko) Chrome/24.0.1309.0 Safari/537.17'
]

在setting.py文件中启用DOWNLOADER_MIDDLEWARES，并且把默认的注释掉

DOWNLOADER_MIDDLEWARES = {

    #'amazon.middlewares.MyCustomDownloaderMiddleware': 543,

    'amazon.middlewares.MyUserAgentMiddleware': 543,
}

在middlewares.py文件中增加以下代码：

rom scrapy.downloadermiddlewares.useragent import UserAgentMiddleware
from amazon.settings import UserAgentList
import random

class MyUserAgentMiddleware(UserAgentMiddleware):

    def __init__(self, user_agent=''):

        self.user_agent = user_agent


    def process_request(self, request, spider):

        agent = random.choice(list(UserAgentList))

        request.headers['User-Agent'] = agent

1.2.2  利用fake-useragent库设置User-Agent方法

安装fake-useragent库(useragent的库)

pip install fake-useragent

在middlewares.py文件中导入fake-useragent库

from fake_useragent import UserAgent

在middlewares.py文件中编写一个middleware中间件，

from fake_useragent import UserAgent
from scrapy.downloadermiddlewares.useragent import UserAgentMiddleware

class MyUserAgentMiddleware(UserAgentMiddleware):

    def __init__(self, user_agent=''):

        self.user_agent = user_agent


    def process_request(self, request, spider): 

        ua = UserAgent()

        request.headers['User-Agent'] = ua.random

在setting.py文件中启用DOWNLOADER_MIDDLEWARES，并且把默认的注释掉

DOWNLOADER_MIDDLEWARES = {

    #'amazon.middlewares.MyCustomDownloaderMiddleware': 543,

    'amazon.middlewares.MyUserAgentMiddleware': 543,
}