def dateRange(start, end, step=1, format="%Y-%m-%d"):
    strptime, strftime = datetime.datetime.strptime, datetime.datetime.strftime
    days = (strptime(end, format) - strptime(start, format)).days
    return [strftime(strptime(start, format) + datetime.timedelta(i), format) for i in xrange(0, days, step)]

ef weekend():
    try:
        dayday = dateRange(st, ed)

        for day in dayday:
            d =day.replace('-','')
            date = d
            server_url = "http://www.easybots.cn/api/holiday.php?d="

            vop_url_request = urllib2.Request(server_url + date)
            vop_response = urllib2.urlopen(vop_url_request)

            vop_data = json.loads(vop_response.read())

            if vop_data[date] == '1' or vop_data[date] == '2':
                dayday.remove(day)

        return dayday

    except:
        dayday = dateRange(st, ed)
        return dayday

有這樣一個weekend函數，去請求一些內容，但是每次執行出來會缺失一些內容懷疑是網速的問題，該怎麼限制遍歷時的頻率或者幾秒內訪問一次呢？