This is wonderful, I love it. I recently wrote a blog post about generating HTML in Python using LXML (https://ricardoanderegg.com/posts/python-build-html-componen...) and I didn't know about your library. I'll update it to add a mention to it.

Apart from the simplicity, I like the fact you can "install" it by copy-pasting the code at the top of your script, or running:

  curl -L https://raw.githubusercontent.com/j4mie/hotmetal/main/hotmetal/__init__.py >> myscript.py

which is nice when you want a self-contained file.

I think I'll be using this in the future.