unable to send command from python to arduino over usb

Hi

I was wondering if someone could help.
I have a couple of arduinos I have been sending messages to from my linux computers USB using a python script.
and everything has been working fine.

my computer mother board failed so I have replaced it with a banana pi bit like a raspberry pi.
running the bananian OS which is a minimal debian OS but this computer has no running desktop so I am unable to open the arduino ide program.as there is no x system installed.

I have the arduino software and python software needed installed but I am unable to communicate with the arduino.
the arduino is attached over usb as device
18.051417] usb 2-1: FTDI USB Serial Device converter now attached to ttyUSB0
and /dev/ttyUSB0

but if I run the python script that I have used before.
I get "Trying... /dev/ttyUSB0
Failed to connect on /dev/ttyUSB0"

The python script will try all serial ports. but it is unable to communicate with the arduino board.

but if I use the same board with the same code on my laptop with the same python script everything works fine.

So I am fairly sure its a problem with the bananian operating system. the only difference I can see is on my laptop and my old PC I opened the arduino IDE and selected the board and serial port.
and after that the IDE software was not used.

But with this new OS I am unable to open the IDE program and select the board and serial port.
Is there a way of doing this by command line.

Please dose anyone have any ideas to help me diagnose the problem.

Thanks

Update

I have just been reading and have just run "sudo chmod 666 /dev/ttyUSB0" to change the permissions.

now the python script communicate but hangs.

simon72post:
now the python script communicate but hangs.

More reading, I suspect.

This does not seem to be an Arduino problem.

...R