Let's Make Robots!

Do I need a compass for autonomous car navigation?

I'm working on building an autonomous car using a 1/10 scale RC car as my platform.  Right now I've got a GPS and 3 axis gyro scope for navigation.  

I'm wondering if I need to add a compass too? 

Sending serial from python to an arduino

I'm working on a project where I send a bunch of data through an arduino to my laptop.  I'm using python serial to read in the serial data.  That part is working fine.  Then I do some processing and I want to send the results back to the arduino.  This part is not working so well.  

It seems like python  serial.write()  only likes to send strings?  Right now I'm trying to send back one integer value.  Any ideas how to do that?