I'm making a code where the pi gets a serial input from a usb-serial board(From the sparkfun RFID starter kit), how can I make this work?

error
Traceback (most recent call last):
   File "main", line 22, in 
    ser = s.Serial('ttyUSB0', 9600, timeout=10000)
   File "/usr/lib/python2.7/dist-packages/serial/serialutil.py", line 260, in init
self.open()
File "/usr/lib/python2.7/dist-packages/serial/serialposix.py", line 276, in open
     raise SerialException("could not open port %s: %s" % (self._port, msg))
  serial.serialutil.SerialException: could not open port ttyUSB0: [Errno 2] No such file or >directory: 'ttyUSB0'

The RFID port is the ttyUSB0
It's the cable. Check the USB cable. All of that yanking
ttyUSB0 not found on Raspberry Pi