serial.serialutil.SerialException: could not open port /dev/ttyACM0

If you try the steps in the post "Talk with Arduino Due in Python Shell" in Linux (Ubuntu in my setup). May be you will be complained with the error of:

serial.serialutil.SerialException: could not open port /dev/ttyACM0: [Errno 13] Permission denied: '/dev/ttyACM0'

Because your user account have no right to access the /dev/ttyACM0 port. You have to add your user account to the dialout group. Enter the command in Terminal:

$sudo usermod -a -G dialout <username>

After you plug in the usb cable, run the command (it need to be run every time plug-in):

$sudo chmod a+rw /dev/ttyACM0

serial.serialutil.SerialException