I move it to GUI section because it's more Tkinter question - what is returned by ListBox.size() rather than anything else. Also, we don't see where itembox is defined, i.e. we don't know is it listbox indeed
If you can't explain it to a six year old, you don't understand it yourself, Albert Einstein
How to Ask Questions The Smart Way: link and another link
Create MCV example
Debug small programs
How to Ask Questions The Smart Way: link and another link
Create MCV example
Debug small programs