pura - the little async embedded visualization framework that could

Pura is a framework enabling remote, always-available graphical and command line views for developers to understand, inspect, and modify their async app while it's running.

During development, it's productive to have visualizations that let you see and alter the internal state of your program. Pura lets you create these easily alongside your regular code, and view them remotely from a web browser. This is especially handy for apps that don't otherwise have a GUI, or run on a device lacking a display.

Visualizations:

apps can register one or more animated graphical views
views are coded using a subset of the Processing API
views can be observed over HTTP by one or more browser clients
views have no overhead unless there is a remote client specifically observing it
keyboard and mouse input is supported

Read-eval-print loop:

apps can register a REPL exposing a specific namespace
REPL instances can be created remotely over HTTP by one or more browser clients
the REPL is available while your program is running
tab completion is supported

Async makes inspection of a running program possible due to the nature of cooperative multitasking: tasks yield only when at a good stopping point. Thus, when a visualization is generated, or a REPL statement evaluated, the program is likely to be in a coherent state honoring its invariants.

The example in action:

Installation

git clone https://github.com/groove-x/pura.git
cd pura
pip install -e .

If you use Trio rather than asyncio:

pip install -e .[trio]

Run the examples

python examples/web_view_example.py

Then connect at http://localhost:8080/

python examples/web_repl_example.py

Then connect at http://localhost:8080/repl

The examples use asyncio by default. For Trio, use --async-backend trio.

Using pura in your own project

Pura requires that your program be fully async (either asyncio or Trio). In other words, the main thread should not be blocked by I/O or computation for any length of time.

Add visualizations to your program by inheriting from WebViewMixin and implementing the draw() method.

At the top level of your program, launch the web view server and register your class instances.

import asyncio
from pura import WebViewMixin, WebViewServer

class Foo(WebViewMixin):
    def __init__(self):
        super().__init__(webview_size=(320, 240))

    def draw(self, ctx):
        ctx.background(0)
        ctx.line(0, 0, ctx.width, ctx.height)
        ...

...

foo = Foo()
server = WebViewServer()
await asyncio.gather(
    server.serve("Web view server", "localhost", 8080),
    foo.webview.serve(server))

See the project examples/ directory, as well as help documentation on the pura package and individual classes.

Disclaimer

Pura is intended to be used over a trusted network to visualize and alter the internal state of a program during development. The web client is implemented via eval of JavaScript received over HTTP from the server.

This software is not supported by GROOVE X, Inc., and GROOVE X specifically disclaims all warranties as to its quality, merchantability, or fitness for a particular purpose.