user23850: Is it possible to have bidirectional communication betweeen an Arduino Uno Rev 3 and a Raspberry Pi Modell B+ running Rasbian? They're connected ofer USB, and it would be good if I could use Python on the Pi.

user20245: Yes.  The Arduino Uno implements a serial protocol inside the USB signal using hardware.  This is how it is built.  The Linux side is a bit more complex as there are many USB protocols.  Here is a howto which talks about the Linux side of the Arduino / Linux connection.  
To be clear, Rasbian is a derivative of Linux.

23850: <p>Is it possible to have bidirectional communication betweeen an Arduino Uno Rev 3 and a Raspberry Pi Modell B+ running Rasbian? They're connected ofer USB, and it would be good if I could use Python on the Pi.</p>
 20245: <p>Yes.  The Arduino Uno implements a serial protocol inside the USB signal using hardware.  This is how it is built.  The Linux side is a bit more complex as there are many USB protocols.  Here is a <a href="http://playground.arduino.cc/Interfacing/LinuxTTY" rel="nofollow">howto</a> which talks about the Linux side of the Arduino / Linux connection.  </p>

<p>To be clear, Rasbian is a derivative of Linux.</p>
