下面是代码：

#! /usr/bin/env python
#-*- coding : utf-8 -*-

import requests
from bs4 import BeautifulSoup
import time
import pymongo    #操作数据库

client = pymongo.MongoClient('localhost',27017)    #连接数据库
xiaozhu = client['xiaozhu']    #建立数据库xiaozhu
fangzi = xiaozhu['fangzi']    #在xiaozhu数据库中建立数据表fangzi

def get_fangzi_url():    #定义函数获取房子信息地址
    urls = ['http://bj.xiaozhu.com/search-duanzufang-p{}-0/'.format(i) for i in range(1, 2)]
    fangzi_list = []
    for url in urls:
        web_data = requests.get(url)
        web_data.encoding = 'utf-8'
        soup = BeautifulSoup(web_data.text, 'lxml')

        for fangzi_urls in soup.select('#page_list > ul > li > a'):
            fangzi_list.append(fangzi_urls['href'])
    return fangzi_list

def get_info_and_insert():    #定义函数获取房子信息并入库
    urls = get_fangzi_url()
    for url in urls:
        web_data = requests.get(url)
        web_data.encoding = 'utf-8'
        content = web_data.text
        soup = BeautifulSoup(content,'lxml')

        fangzi_info = {}    #定义字典，存放房子信息

        fangzi_info['title'] = soup.select('em')[1].text
        fangzi_info['area'] = soup.select('.pr5')[0].text.strip()
        fangzi_info['price'] = soup.select('#pricePart .day_l span')[0].text

        fangzi.insert_one(fangzi_info)    #入库
        print(url)    #随意打印点信息，刷存在感
        time.sleep(2)    #慢慢来，休息2秒，防止封爬虫

def find_fangzi():    #定义函数筛选房源
    for info in fangzi.find():
        if int(info['price']) >= 300:
            print(info)
#get_info_and_insert()    #执行获取并入库

find_fangzi()

关键点：

• 确定信息地址
• 数据库操作
• 终于学会了markdown引用代码了，原来是键盘左上角tab键上面那个小点