时间差

def time_diff(close_time_str, open_time_str):
    """计算关闭时间与打开时间的时间差"""
    if close_time_str == '':
        return None
    ct_date = datetime.datetime.strptime(close_time_str, '%Y-%m-%d %H:%M:%S')
    ot_date = datetime.datetime.strptime(open_time_str, '%Y-%m-%d %H:%M:%S')
    minutes = (ct_date-ot_date).seconds/60
    return round(minutes, 2)