serial中python通信

# ! /usr/bin/env python
# -*- coding: utf-8 -*-
import sys
import time
reload(sys);
sys.setdefaultencoding("utf-8")
import serial
# 导入串口模块
import threading
import time
import serial
ser = serial.Serial("COM3",115200)
send = ser.write("\n")
send = ser.write("\n")
time.sleep(2)
send = ser.write("root")
send = ser.write("\n")
print ser.portstr
print send
time.sleep(2)
send = ser.write("nE7jA%5m")
send = ser.write("\n")
print send
time.sleep(2)
send = ser.write("export")
send = ser.write("\n")
print send
time.sleep(2)
data = ""
while ser.in_waiting > 0 :
    data+=ser.read(1)
if data != "":
    print data