Doing it inside <script type="text/python">…</script>, and having the library scan for such elements, has been a standard technique in such situations for over

Doing it inside <script type="text/python">…</script>, and having the library scan for such elements, has been a standard technique in such situations for over two decades (and for stylesheet languages, like <style type="text/less">…</style>). Doing it inside a custom element like <py-script>…</py-script> has been done occasionally, but doesn’t work well because (a) the code is now visible in the document by default and only hidden by stylesheets, and (b) < and & now need to be escaped as < and &amp;.