scrapy中的request

scrapy中的request
初始化参数
class scrapy.http.Request(
url [ ,
callback,
method='GET',
headers,
body,
cookies,
meta,
encoding='utf-8',
priority=0,
 don't_filter=False,
 errback ] )

1，生成Request的方法
def parse_page1(self, response):
    return scrapy.Request("http://www.example.com/some_page.html",
                          callback=self.parse_page2)

def parse_page2(self, response):
    # this would log http://www.example.com/some_page.html
    self.logger.info("Visited %s", response.url)

2，通过Request传递数据的方法
def parse_page1(self, response):
    item = MyItem()
    item['main_url'] = response.url
    request = scrapy.Request("http://www.example.com/some_page.html",
                             callback=self.parse_page2)
    request.meta['item'] = item
    yield request

def parse_page2(self, response):
    item = response.meta['item']
    item['other_url'] = response.url
    yield item

3，Request.meta中的特殊关键字

4,主要子类FormRequest,用于登陆
return [FormRequest(url="http://www.example.com/post/action",
                    formdata={'name': 'John Doe', 'age': ''},
                    callback=self.after_post)]

更相信的登陆的例子
import scrapy

class LoginSpider(scrapy.Spider):
    name = 'example.com'
    start_urls = ['http://www.example.com/users/login.php']

    def parse(self, response):
        return scrapy.FormRequest.from_response(
            response,
            formdata={'username': 'john', 'password': 'secret'},
            callback=self.after_login
        )

    def after_login(self, response):
        # check login succeed before going on
        if "authentication failed" in response.body:
            self.logger.error("Login failed")
            return

        # continue scraping with authenticated session...