Inline Python where all you have to do is put in <python></python>

You can do that today with PyScript:

  <script type="module" src="https://pyscript.net/releases/2025.8.1/core.js"></script>
  <py-script>
  import sys
  from pyscript import display
  display(sys.version)
  </py-script>

Demo: https://static.simonwillison.net/static/2025/pyscript-demo.h...

Or you can use MicroPython which is much smaller:

    <mpy-script>
      import sys
      from pyscript import display
      display(sys.version)
    </mpy-script>

Demo: https://static.simonwillison.net/static/2025/pyscript-microp...

Since they compiled the python interpreter to webassembly, yes you can now totally do a <python></python> webcomponent if you like. Of course it requires the extra work of importing this interpreter. Web browsers aren't going to come with multiple interpreters built-in, it would be too heavy.

I would be interested to see how short the time to run "Hello World" can be with python in a webpage, counting the time to load the whole page without cache.

Try benchmarking https://static.simonwillison.net/static/2025/pyscript-microp... and see. It's pretty minimal.

What kind of safeguards would we need in place with this sort of feature in html? What are the security implications?

DOM access without JS interop?