Since upgrading my computers to Ubuntu 13.10 (or Xubuntu 13.10), I have been unable to use Python's IDLE interpreter.
Fortunately there's a simple fix... edit /usr/lib/python2.7/idlelib/IOBinding.py (as root) and change line 128 from:
str = str.split("\n", 2)[:2]
lst = str.split("\n", 2)[:2]
Or simply apply the attached patch to the .py file using:
sudo patch /usr/lib/python2.7/idlelib/IOBinding.py -i idlefix.patch