[Tkinter] What is this error?

[deanhystad]

I don't get an error when I run your code. It doesn't do anything interesting when the search button is pressed. but there is no error.

You cannot set a widget's parent using the config command.

result_lbl = Label()
result_lbl.config(results, text = "Physical quantity")

You need to specify the parent when you create the widget.

results = LabelFrame(main, text = "Results")
result_lbl = Label(results)

If you want to hide or pop up a widget inside a window you can use pack and forget.