Python：如果发生超时，请尝试上载三次

Question

我正在将图像文件上传到服务器，但是当超时发生时，它会终止上传并移动到下一个。如果发生超时，我想再次上传图像。我想尝试在最大上传三次，并且在三次尝试后如果仍然发生超时则抛出异常然后移动到下一个。

这是我的代码

def upload(filename2,sampleFile,curr_time,curr_day,username,password,user_id):

    register_openers()
    datagen, headers = multipart_encode({"sampleFile": open(sampleFile), "name": filename2, "userID": user_id,'date': curr_day,'time': curr_time, 'username': username,'password': password})

    request = urllib2.Request("http://videoupload.hopto.org:5001/api/Synclog", datagen, headers)

    try:
        response = urllib2.urlopen(request, timeout = 20)
        html=response.read()                
    except URLError , e:
        if hasattr(e, 'reason'):
            print ('Reason: ', e.reason)                
        elif hasattr(e, 'code'):
            print ('Error code: ', e.code)
    except Exception:
        print ('generic exception: ' + traceback.format_exc())
    return