How are you supposed to start Tkinter?
I know this is old, but it helped me solve this. I am also on Windows 10.You have to run a native X server. See the answer here from @speaker-to-animals.The os.environ command above is the same as SET DISPLAY=:0.0 from CMD.Start the Xorg server on your Windows box, with no client, so it is waiting in the background.With this setup, your code above works exactly as you want it to. I ran it from the Windows CMD, not Cygwin. I use this to add GUI to test cases - the testers like it.