I guess if you can run `python myfile.py` and it finishes with without error (return code 0), you could consider it valid.

By that measure, there are also 1 byte valid Python programs (e.g. "1").

But (at least for Python) that test also works on empty (0 byte) files, which is presumably why the repository says an empty file is the smallest possible Python program, but which feels wrong to me somehow.

Yes, that was my point. And thus “also” for 1 byte programs