FastHTML – Modern web applications in pure Python

Very cool! After trying different approaches to render HTML from Python objects (including lxml, xml, etc.) I ended up liking htpy[0] the most, and the apps I built look similar to the examples in the FastHTML docs. I'll definitely try it.

One pattern I use is putting all the functions that generate HTML inside their own class. That way, I can more easily create and reuse components like:

  class Views:
      ...

  def comp1(self):
      return Div(self.header(), P("too"))

Then `self.header()` can be reused in other parts, or to return partial HTML. It also makes it easy to pass the "request" object to the class, and do conditional rendering based on it (cookies, auth, language, etc).

[0]: https://htpy.dev/

Yes htpy is nice! Other interesting examples of functional HTML include Elm-html (Elm), hiccl (Common Lisp), hiccup (Clojure), Falco.Markup (F#), Lucid (Haskell), and dream-html (OCaml). FastHTML's system, called "FastTag" (FT) is a bit of a mashup of all of them plus some extra bits. I seriously considered just using htpy actually -- but in the end decided I preferred something a little different.

I've wondered about a class-based approach like that -- interesting to hear it's worked for you. I should try it! I'm using a purely functional approach for re-use, as you see in this example of the code for about.fastht.ml:

https://github.com/AnswerDotAI/fh-about/blob/main/overview.p...

One check I always like to do with a new Python-based framework is this - does it support the creation of a dynamic number of components at runtime, AND each having their own component state? Most frameworks I've tried support one or the other, but not both. Is there an example that demonstrates something like this in FastHTML - user provides a number n at runtime, n cards are generated, each card has its own text field which can be modified by the user without affecting the other cards' text fields.

In this case, it's a 1:1 mapping to what's on the page, so your concern doesn't apply here. Debugging and refactoring is far easier with Python functions than templates, and CSS programmers just use CSS the usual way.

To answer your question, I'll quote from https://about.fasht.ml:

Templates were originally created for web development in the 1990s, back when web design required complex browser-specific HTML. By using templates, designers were able to work in a familiar language, and programmers could “fill in the blanks” with the data they needed. Today this is not needed, since we can create simple semantic HTML, and use CSS to style it.

Templates have a number of disadvantages, for instance:

- They require a separate language to write the templates, which is an additional learning curve

- Template languages are generally less concise and powerful than Python

- Refactoring a template into sub-components is harder than refactoring Python code

- Templates generally require separate files

- Templates generally do not support the Python debugger.

By using Python as the HTML-generation language, we can avoid these disadvantages. More importantly, we can create a rich ecosystem of tools and frameworks available as pip-installable Python modules, which can be used to build web applications.

The home page was running on a $5/month hobby account at launch today and reached 1% use of 1 VCPU -- so speed seems pretty good to me! Having said that, not all the example apps are well optimised, since we're aiming largely to teach the basics.

I'd love to see gradio-style components written in FastHTML -- I actually raised this idea with the founder of gradio today. It would be a great combo IMO.