scrapy的allowed_domains设置含义

#/usr/bin/env python
#coding:utf-8
import scrapy
# import sys
# import os
from scrapy_study.items import DemoItem

class DemoScrapy(scrapy.Spider):
    name = ‘demoscrapy‘
    
    # start_urls = [‘http://scrapy-chs.readthedocs.io/zh_CN/1.0/intro/tutorial.html‘]
    allowed_domains = ["scrapypython.2org"]
    # start_urls = [‘https://docs.python.org/2/library/os.path.html‘]
    start_urls = [‘http://yogoup.sinaapp.com/‘]
    def parse(self,response):
        print response.body