I get an error every time I hit build even with the simplist hello world program.
python3: can’t open file ‘sfile’: [Errno 2] No such file or directory
[Finished in 0.0s with exit code 2]
[cmd: [‘python3’, ‘-u’, ‘sfile’]]
[dir: /home/sean/.config/sublime-text-3/Packages/User]
[path: /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin]
It worked a day ago. I just started using it then.
It doesn’t look like you’ve saved the file with a .py extension, or perhaps not saved the file at all.
I think Sublime has a feature that saves all buffers automatically, internally. So when you open again Sublime, things are exactly as they were when you left the workspace last time. This is really neat, I love this feature personally, but it could cause something like described there. Hope you get things going, let us know 
A FB forum saved me.
I copied from the book, use {} as begin and end, and failed.
Or maybe this was a later try.
Anyway, thanks, you were a help.