If you're just modifying an existing python app, install it on your tablet and make the changes there. A few of us actually do all of our development on-device.

You can also use ssh to connect to your device and edit the code on your desktop and then run it on the device. The Ubuntu Gnome desktop can even connect to your tablet using the "connect to server" in the Places menu, and then you can browse and edit the files like a local drive.

But, yeah, if you want to develop entirely on a desktop machine, and only move to the device when you've got a finished package, you'll probably want the SDK (ie scratchbox) to emulate the Maemo environment.