如何避免Tkinter中未处理的异常？

Question

I'm trying to exit my program when the user decides to close the Tkinter filedialog menu without selecting a file to open. However, although the program exits I keep getting the following message before it terminates:

The debugged program raised the exception unhandled FileNotFoundError [Errno2] No such file or directory

I thought the code I have below would handle something like that though, but maybe I am wrong? Any help or advice would be appreciated.

if root.fileName is None:
    sys.exit(0)
else:
    pass

Answer 1

When it doesn't return a filename (the user canceled the dialog), filedialog will return an empty string ( '' ), not None . Use this instead:

if not root.fileName:
    ...

Answer 2

I have never used tkinter but it seems that even though no file was selected by the user the file dialog it is still trying to look for a file. In general when handling exception you would place the relevant code in a try except block.
EG you may have to import the exception from tkinter for the below to work

   try:
    # code that can throw an exception
    if root.fileName is None:
        sys.exit(0)
    else:
        pass
except FileNotFoundError:
    # add code on how you want the error handled
    pass

for more details on exception handling have a look at the doc's here