python - 在 Scrapy 类中定义附加方法

Question

Scrapy 类是如何执行的以及如何向蜘蛛类添加其他方法？

例如，来自文档:

import scrapy

class DmozSpider(scrapy.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] + '.html'
        with open(filename, 'wb') as f:
            f.write(response.body)

如果我想定义一些方法来轮询数据库或其他东西，我该怎么做，为什么？

Answer 1

让我们看一下以下用例 - 从数据库获取要爬网的 URL。为此，您需要使用 start_requests() method 而不是 start_urls .

示例代码(直接使用MySQLdb驱动程序):

import MySQLdb
import scrapy

class DmozSpider(scrapy.Spider):
    name = "dmoz"
    allowed_domains = ["dmoz.org"]

    def start_requests(self):
        db = MySQLdb.connect(host="host", user="user" ...) 
        cursor = db.cursor()

        cursor.execute("SELECT url from url_table")
        requests = [scrapy.Request(url=row[0]) for row in cursor.fetchall()]

        cursor.close()

        return requests

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