detect tk mainloop

[John Hunter]

In matplotlib using the tkagg backend, the tk mainloop is started at
the end of a python script by issuing a call to a "show" function,
which realizes all the created figure windows and the calls
Tkinter.mainloop().  This can cause problems if the mainloop was
started by another module (eg idle).

Is there a way to query tkinter to detect whether the mainloop has
already been called?

Thanks,
JDH