Scrapy学习-12-使用DownloaderMiddleware随机修改User-Agent

随机替换请求头中的User-Agent

基于github开源项目，实现User-Agent的动态切换和管理

 https://github.com/hellysmile/fake-useragent

 

fake-useragent维护不同User-Agent的字段值

 https://fake-useragent.herokuapp.com/browsers/0.1.8

middlewares.py

from fake_useragent import UserAgent

class RandomUserAgentMiddlware(object):
    def __init__(self, crawler):
    super(RandomUserAgentMiddlware, self).__init__()
    self.ua = UserAgent()
    self.ua_type = crawler.settings.get("RANDOM_UA_TYPE", "random")

    @classmethod
    def from_crawler(cls, crawler):
        return cls(crawler)

    def process_request(self, request, spider):
        def get_ua():
            return getattr(self.ua, self.ua_type)

        request.headers.setdefault('User-Agent', get_ua())

配置settings中downloader middleware的优先级

DOWNLOADER_MIDDLEWARES = {
    'ArticleSpider.middlewares.JSPageMiddleware': 1,
    'ArticleSpider.middlewares.RandomUserAgentMiddlware': 543,
    'scrapy.downloadermiddlewares.useragent.UserAgentMiddleware': None,
}
RANDOM_UA_TYPE = "random"