try / except语句的最佳解决方案

Question

我想知道try try语句的这种定义是否将具有正确的行为，以及是否有更可靠的解决方案。读取功率计是一种定义，基本上，如果COM被锁定或接合，我希望实现第二个异常块，并且功率计响应具有响应“毛刺”，例如，我希望对第一个异常块实现值错误

def get_power_meter():

    try:
        pm = serial.Serial(pm_com_open, 115200, timeout = 1)
        pm.write(b'PW?\r')
        pm_res = pm.readline().decode("utf-8")
        pm.close()            
        return float(pm_res)        

        try:
            pm = serial.Serial(pm_com_open, 115200, timeout = 1)
            pm.write(b'PW?\r')
            pm_res = pm.readline().decode("utf-8")
            pm.close()            
            return float(pm_res)

        except ValueError as e:
            time.sleep(1)
            print(e)

    except serial.serialutil.SerialException:
        message_box_ok(pm_com_open + " is locked...","Please press OK to to restart the software","Aborting...",sys.exit(0),"warning")