The default Python on OS X shouldn't be played with as it's utilized by the OS itself. On the off chance that your default is 2.6.1, at that point you should have Snow Leopard.
On the off chance that you simply introduce from the standard 3.1 circle picture, at that point you can summon it utilizing python3.1 from the terminal (you don't need to do any additional means for this to work) and you can leave the plain python as 2.6.1.
Want to know more about python? Come and Join: python certification course