Xubuntu - How I ruined and saved my day at the same time

Last Saturday, When I was trying to install some packages in my laptop which is Xubuntu 13.04, I accidentally remove some python packages and... It's just so fast when I couldn't hold my finger from stopping pressing ENTER. "CTRL+ C", "CTRL+X" couldn't help me. I rebooted, the screen kept checking my laptop's battery condition... I couldn't log-in anymore.

I googled around, and found some solutions which was useless in my case:

* Solution 1: Boot to the recovery mode of Xubuntu, run the root shell, install GDM and used it as the default display manager instead of LightDM:

# apt-get install gdm
# dpkg-reconfig gdm
# reboot

=> The GDM's log-in screen appear, I enter my account information => Xubuntu couldn't find any GNOME session. I switched back to lightdm.
=> Fail.

* Solution 2:  Boot to the recovery mode of Xubuntu, select the fix broken packages line in the menu, restart

=> nothing changed.

And then, I decided to re-install the complete XFDE desktop, in the recovery mode of Xubuntu, root shell:

# apt-get install --reinstall xubuntu-desktop

restart, It worked, everything's back!!!! (Actually I had to reinstall ibus-unikey)