Use Python

A Python scripts runner composable. Run Python scripts in a Pyodide service worker

Install

As a package

npm install usepython
# or
yarn add usepython

Then use it:

import { usePython } from "usepython";

const py = usePython();

As script src

    <script src="https://unpkg.com/[email protected]/dist/py.min.js"></script>
    <script>
      const py = $py.usePython();
    </script>

As script type module

    <script type="module">
      import { usePython } from "https://unpkg.com/[email protected]/dist/py.esm.js";
      const py = usePython();
    </script>

Usage

Load the runtime

Load the Python runtime:

await py.load()

Listen to the install log:

const unbindInstallLog = py.installLog.listen((val) => {
  console.log(`Installing Python, stage ${val.stage}: ${val.msg}`)
})
await py.load();
unbindInstallLog();

The install log object is a nanostore

Load libraries

It is possible to install some Python packages: either packages built for Pyodide, standard pip packages that will be installed with Micropip, or custom wheels

const wheel = '/acustomwheel-0.0.1-py3-none-any.whl';
const pyodideLibs = ['pandas', 'numpy', 'bokeh'];
await py.load(pyodideLibs, ['altair', wheel, 'vega_datasets'])

Run Python code

Run some sync Python code:

const script = `a=1
b=2
a+b`
const { result, error } = await py.run(script);

The result is the last line of the script, just like a return value

See the documentation

To run async code use the runAsync function.

Namespaces

An optionnal namespace parameter can be used to isolate Python contexts:

const { result, error } = await py.run("a=1", "ns1");

The variable defined in the script will be accessible only in the same namespace:

const { result, error } = await py.run("b=a+1", "ns1");

To flush the context of the namespace and reset all user defined variables use the clear function:

await py.clear("ns1");

Listen to stdout

Listen to the Python stdout output:

py.log.listen((val) => {
  console.log("LOG", val.stdOut)
  // val.stdErr is also available
});
const script = `print('ok from python')`;
await py.run(script);

The log object is a nanostore

State

Atom stores are available to listen to the ready state and execution state of Python. Example:

py.isReady.listen((v) => console.log("Ready state:", v));
py.isExecuting.listen((v) => console.log("Execution state:", v));

Vuejs example:

import { useStore } from '@nanostores/vue';

const isExecuting: Readonly<Ref<boolean>> = useStore(py.isExecuting);
const isReady: Readonly<Ref<boolean>> = useStore(py.isReady);

Examples

• Script src
• Script module
• Vuejs