scrapy-继承默认的user-agent 中间件

class MyUserAgentMiddleware(UserAgentMiddleware):

    def __init__(self, user_agent):
        self.user_agent = user_agent

    @classmethod
    def from_crawler(cls, crawler):
        o = cls(Faker())
        crawler.signals.connect(o.spider_opened, signal=signals.spider_opened)
        return o

    def process_request(self,request,spider):
        request.headers.setdefault('User-Agent',self.user_agent.user_agent())

　　

配置

DOWNLOADER_MIDDLEWARES = {
   #'middle.middlewares.MyCustomDownloaderMiddleware': 543,
   'middle.middlewares.MyUserAgentMiddleware': 100,
   'scrapy.downloadermiddlewares.useragent.UserAgentMiddleware': None,
}

注意 @classmethod不能删除 

#!/usr/bin/python
# -*- coding: UTF-8 -*-

class A(object):
    bar = 1
    def func1(self):
        print ('foo')
    @classmethod
    def func2(cls):
        print ('func2')
        print (cls.bar)
        cls().func1()   # 调用 foo 方法

A.func2()               # 不需要实例化