'modal dialogs' with Tkinter

[Birdman]

You could try using: EasyGUI    http://www.ferg.org/easygui/

 EasyGUI is different from other GUIs in that EasyGUI is NOT
event-driven. It allows you to program in a traditional linear fashion,
and to put up dialogs for simple input and output when you need to. If
you have not yet learned the event-driven paradigm for GUI programming,
EasyGUI will allow you to be productive with very basic tasks
immediately. Later, if you wish to make the transition to an
event-driven GUI paradigm, you can do so with a more powerful GUI
package such as anygui, PythonCard, Tkinter, wxPython, etc.

It works for me and is easy to modify to your needs.