> This is good. But the title mentioned dataclasses, and they are 3.7+.

Ahh, sorry, I think now I understand you. :-)

Indeed, when I switch to the branch with that change (https://github.com/gnprice/cpython/commit/2b4aec4dd -- it comes after the patch that's GH-15248, so I haven't yet sent it as a PR), then `python3.6 Tools/unicode/makeunicodedata.py` no longer works.

I think this is fine. Most of all that's because this always works:

    ./python Tools/unicode/makeunicodedata.py

Anyone who's going to be running that script will want to build a `./python` right afterward, in order to at least run the tests. So it doesn't seem like much trouble to do the build first and then run the script (and then a quick rebuild for the handful of changed files), if indeed the person doesn't already have a `./python` lying around.

In fact `./python` is exactly what I used most of the time to run this script when I was developing these changes, simply because it seemed like the natural thing to do.