python下载网页源码 写入文本

import urllib.request,io,os,sys
req=urllib.request.Request("http://echophp.sinaapp.com/uncategorized/194.html")
f=urllib.request.urlopen(req)
s=f.read()
s=s.decode('utf-8','ignore')
mdir=sys.path[0]+'/'
file=open(mdir+'html.txt','a',1,'gbk')
file.write(s)
file.close()