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pyrract Add state! Apr 21, 2017


Pyrract is a React-esque library for Python. It allows you to build component trees with a simple DSL.

Our primary target is currently Toga, an emerging widget toolkit for desktop (Windows, Linux and macOS) and mobile (Android and iOS). (It is still in development, but already usable — see the platform support page).

Let's run a quick demo.

class Root(Component):
    def __init__(self, **props):
        self.state = {"count": 0}

    def do_count(self, widget):
        self.set_state(lambda s: {"count": s["count"] + 1})

    def render(self):
        return TogaBox() [
            TogaButton(label="Needs some pudding, huh"),
            # [TN: pudding means padding, see]
            TogaButton(label="Clicked %d times" % self.state["count"],

app = toga.App(name="TEM COUNTER!!!", app_id="rocks.ale.TemCounter",
               startup=lambda app: render(Root()).base)

If you've seen React, you'll instantly recognize what's going on here.

To try out this code, run:

pip install toga
git clone && cd pyrract
python -m pyrract.demo

Now click that button. C'mon. That's all I've got.



  • You can't remove elements apparently (see pybee/toga#30).

    • Either wait when it's fixed...
    • ...try fix it ourselves...
    • ...or move on to something a bit more stable, like Qt / PySide?
  • Needs performance testing. I'm using suboptimal tree comparison

Prior art

Pyrract is heavily inspired, loosely based on Preact, a fast, lightweight React-compatible JavaScript library. It is totally awesome.



Final thoughts

Fish can't understand what the actual fuck am I doing