python 爬虫 发送每天天气 - 爬虫的流程

#!/usr/bin/python
# -*- coding: UTF-8 -*-
import requests,bs4,smtplib,sys
import smtplib, sys
from email.mime.text import MIMEText
msg_from='linuxdxw@163.com' #发送方邮箱
passwd='haha' #填入发送方邮箱的授权码
#msg_to='1536175386@qq.com' #收件人邮箱
msg_to='dingxw@onecloud.cn' #收件人邮箱

subject="weather report" #主题
def sent():
　　fileObj = open('/root/port.txt')
　　content=fileObj.read()
　　msg = MIMEText(content)
　　msg['Subject'] = subject
　　msg['From'] = msg_from
　　msg['To'] = msg_to
#try:
　　s = smtplib.SMTP("smtp.163.com",25)
　　s.login(msg_from, passwd)
　　s.sendmail(msg_from, msg_to, msg.as_string())
# print "发送成功"
#except s.SMTPException,e:
# print "发送失败"
#finally:
　　s.quit()

def getweather(pos):
　　headers={'User-Agent': 'Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:24.0) Gecko/20100101 Firefox/24.0'}
　　url='http://www.tianqi.com/guangzhou/'
　　urlhtml=requests.get(url,headers=headers)
　　urlhtml.raise_for_status()
　　weatherhtml=bs4.BeautifulSoup(urlhtml.text[:],'html.parser')
　　weather=weatherhtml.select('a')
　　for i in range(len(weather)):
　　weathnow=weather[i].getText()
　　if i == pos:
　　　　return weathnow

with open('/root/port.txt','w') as f:
　　f.write(getweather(23)+"\n")

with open('/root/port.txt','a') as f:
　　f.write(getweather(35)+"\n"+"\n")
with open('/root/port.txt','a') as f:
　　f.write(getweather(75)+"\n")

sent()

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2. 爬虫的流程 - 程序每次对一个网站执行下载操作，都必须等到前一个网站下载完成后才能开始。

1. 先是遍历存储网站的列表；
2. 然后对当前网站执行下载操作；
3. 等到当前操作完成后，再对下一个网站进行同样的操作，一直到结束。