[Tkinter] function to handle exception errors

[atlass218]

hello;
for more information this picture describe what I want to do for handling exception:

I describe my problem explicitly: when the user writes a string in the "Entry" widget which carries the instruction "enter the value of the DDM read by the plane LABO". this displays the red alert message below the Entry widg (for example you have introduce cataracts and not numbers, please enter decimal numbers). Then once it enters a decimal correct number it appears the result indicates in the block of the try, and at the same time the red message of alarm must be erased.



thanks for help