I'm currently working on a raspberry pi project for school where I read data from an OBD2 to usb censor in my car. 

When I'm using Screen to connect to the serial port everything works fine, but when I try to do it in python the serial.readline() returns an empty string.

Does anybody know how I can retrieve data from the serial port in python? 

I've tried about every option available.

```
import serial

ser = 0

#Function to Initialize the Serial Port
def init_serial():

    global ser         
    ser = serial.Serial()
    ser.baudrate = 38400   
    ser.port = '/dev/ttyUSB0' 
    ser.timeout = 1
    ser.open()          #Opens SerialPort

    # print port open or closed
    if ser.isOpen():
    print 'Open: ' + ser.portstr
    #Function Ends Here

init_serial()

temp = raw_input('Type what you want to send, hit enter:\r\n')
ser.write(temp)         #Writes to the SerialPort

while 1:    
      bytes = ser.readline()  #Read from Serial Port
      print bytes      #Print What is Read from Port

```