python - 用pyserial模块却显示不能打开串口？

我想用串口通信交换数据，但用了COM1，COM2....一直都显示不能打开
用了下面的代码显示无可用PORT，请各位大大帮忙看看

# -*- coding: utf-8 -*
 
import serial
import serial.tools.list_ports
 
port_list = list(serial.tools.list_ports.comports())
 
if len(port_list) <= 0:
    print "The Serial port can't find!"
     
else:
    port_list_0 =list(port_list[0])
 
    port_serial = port_list_0[0]
 
    ser = serial.Serial(port_serial,9600,timeout = 60)
 
    print "check which port was really used >",ser.name