[Python] How to use Python to write and read from serial

#! /usr/bin/env python
# -*- coding: utf-8 -*-
# html_converter version 1.0
import serial
import time

locations=['/dev/ttyUSB0','/dev/ttyUSB1','/dev/ttyUSB2','/dev/ttyUSB3',
'/dev/ttyS0','/dev/ttyS1','/dev/ttyS2','/dev/ttyS3']  

for device in locations:
    try:
        print "Trying...",device
        ser = serial.Serial(device, 115200)
        break
    except:
        print "Failed to connect on",device   

# var = 1
# while var == 1:
#     if ser.inWaiting() > 0:
#       print ser.readline(1024)

print "Enter Newline"
print ser.write('\n')
ser.write('ls')
print ser.read(ser.inWaiting())
print "Enter Newline"
print ser.write('\n')
ser.write('exit')
time.sleep(1)
print ser.write('\n')
print ser.write('\n')