Your code, as posted, works:
File exists
/usr/bin/python2.7 /home/surest/github/tests/test.py
Enter the directory to the ISO file (or just drag the file here): /home/surest/Desktop/duties.odt
/home/surest/Desktop/duties.odt
<type 'str'>
True
Process finished with exit code 0
Typo in filename/path
/usr/bin/python2.7 /home/surest/github/tests/test.py
Enter the directory to the ISO file (or just drag the file here): /home/surest/Desktop/meesa-typoed.odt
/home/surest/Desktop/meesa-typoed.odt
<type 'str'>
False
Process finished with exit code 0
solved os.path.isfile isn’t working as expected