2 threads; 1 more Tkinter and 1 more terminal. problem

[ChrisChia]

Hi all,
i am trying to do a GUI with Tkinter package, but i am stuck no matter
what...
The problem right now is that my GUI has a label= 'A' (where 'A' is
the text on display)

i wish to run a program with 2 threads... one for my GUI and the other
for the terminal where the terminal will keep listening to the user
input (let's say if he enters 'B'), the GUI will update it's label to
'B'.

It's easy to let the terminal wait after the user has entered the
input.
But the problem is that when the GUI loads up... the

root.mainloop()

doesn't seem to release the control, hence my thread cannot work on
GUI.

Is there a way to solve this problem?
2 threads; 1 more GUI and 1 more terminal.