python 使用urllib2获取网页内容时，如何设置超时时间

#获取html内容

#coding=utf8
import socket
import time
import urllib2
import os,sys
import json
socket.setdefaulttimeout(60)    ----设置socket超时时间，60s
def getData(base_url, query=""):
    req_header = {'User-Agent':'Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) \
            Chrome/39.0.2171.71 Safari/537.36', 'Content-Type': 'application/x-www-form-urlencoded'}
    req_timeout = 3    ---使用urllib2库本身自带的超时参数，一般情况下接口设置为3s，网页抓取设置为5s
    url = ""
    if query:
        url = base_url + "&kw=" + urllib2.quote(query)
    else:
        url = base_url
    print url
    req = urllib2.Request(url, None, req_header)
    # print req
    retryTime = 3
    return_dict = {}
    while retryTime > 0:
        try:
            doc = urllib2.urlopen(req, None, timeout=req_timeout).read()
            return json.loads(doc)
        except Exception, e:
            if retryTime == 1:
                # logger.error(str(e)+', url:'+url)


                print 'reTryTime:',retryTime,'\n\n'
                retryTime -= 1
    return return_dict