测试并验证过的代码，希望利于同行们学习和使用：

# -*- coding: utf_8 -*-

import serial

import modbus_tk

import modbus_tk.defines as cst

from modbus_tk import modbus_rtu

def mod(PORT="com2"):

    red = []

    alarm = ""

    try:

        # 设定串口为从站

       # master = modbus_rtu.RtuMaster(serial.Serial(port=PORT,baudrate=9600, bytesize=8, parity='N', stopbits=1))

        master = modbus_rtu.RtuMaster(serial.Serial(port=PORT,baudrate=9600, bytesize=8, parity='N', stopbits=1))

        master.set_timeout(5.0)

        master.set_verbose(True)

        # 读保持寄存器

        red = master.execute(1, cst.READ_HOLDING_REGISTERS, 0, 9)  # 这里可以修改需要读取的功能码

        print(red)

        alarm = "正常"

        return list(red), alarm

    except Exception as exc:

        print(str(exc))

        alarm = (str(exc))

    return red, alarm  ##如果异常就返回[],故障信息

if __name__ == "__main__":

    mod()