Python USB Serial

My previous post was not clear.
What I want to know is how to send serial data out the USB port with Python. The attached code via the shell does not work, and I have verified that the data from the Arduino side is getting to the Linino side. If I comment out the two serial lines (ser = and ser.write) the code runs. And the serial module was installed successfully with pySerial.
Thanks for help and putting up with this.

#!/bin/python


import serial


import sys    
sys.path.insert(0, '/usr/lib/python2.7/bridge/') 

from bridgeclient import BridgeClient as bridgeclient

ser = serial.Serial('/dev/tty.ACM0', 19200)


bridge = bridgeclient()

key = "temperatureNamesKey"
namesFromArduino = bridge.get(key)
print namesFromArduino

key = "temperaturesKey"
temperaturesFromArduino = bridge.get(key)
print temperaturesFromArduino

together = namesFromArduino + "," + temperaturesFromArduino
print together
ser.write(together)