The bug has been opened on https://bugs.launchpad.net/ubuntu/+source/gedit/+bug/104772

"Binary package hint: gedit

this is an interesting bug, it may be common to all gedit, I don't know.

so if you type 1/2 in the console you get the return of:

>>> 0

now, if you then type from __future__ import division

and then type 1/2 you still get:

>>> 0

this should not be happening. Try doing the same thing in command line python console or IDLE, or what have you.

you should be getting 0.5, because you're changing the division type."