在我的python应用程序中,我必须阅读许多网页来收集数据。为了减少http调用,我想只获取更改的页面。我的问题是我的代码总是告诉我页面已被更改(代码200),但实际上并非如此。
这是我的代码:
from models import mytab
import re
import urllib2
from wsgiref.handlers import format_date_time
from datetime import datetime
from time import mktime
def url_change():
urls = mytab.objects.all()
# this is some urls:
# http://www.venere.com/it/pensioni/venezia/pensione-palazzo-guardi/#reviews
# http://www.zoover.it/italia/sardegna/cala-gonone/san-francisco/hotel
# http://www.orbitz.com/hotel/Italy/Venice/Palazzo_Guardi.h161844/#reviews
# http://it.hotels.com/ho292636/casa-del-miele-susegana-italia/
# http://www.expedia.it/Venezia-Hotel-Palazzo-Guardi.h1040663.Hotel-Information#reviews
# ...
for url in urls:
request = urllib2.Request(url.url)
if url.last_date == None:
now = datetime.now()
stamp = mktime(now.timetuple())
url.last_date = format_date_time(stamp)
url.save()
request.add_header("If-Modified-Since", url.last_date)
try:
response = urllib2.urlopen(request) # Make the request
# some actions
now = datetime.now()
stamp = mktime(now.timetuple())
url.last_date = format_date_time(stamp)
url.save()
except urllib2.HTTPError, err:
if err.code == 304:
print "nothing...."
else:
print "Error code:", err.code
pass
我不明白出了什么问题。任何人都可以帮助我吗?
答案 0 :(得分:5)
当您发送“If-Modified-Since”标头时,Web服务器不需要发送304标头作为响应。他们可以自由发送HTTP 200并再次发送整个页面。
发送'If-Modified-Since'或'If-None-Since'警告服务器您希望缓存响应(如果可用)。这就像发送'Accept-Encoding:gzip,deflate'标题 - 你只是告诉服务器你会接受一些东西,而不是要求它。
答案 1 :(得分:0)