PyoNightshade

Pyodide + Web Worker + Matplotlib + Cartopy

A sample project to setup Pyodide with built in packages and a Web Worker, visible at https://pyo-nightshade.vercel.app/.

Below is a brief explaination of the code breakdown.

plot.py

A modified Cartopy Nightshade sample.

If running in Pyodide:

• the drawing is exported to a base 64 string to be loaded as an image in the main thread of the browser
• the AGG Matplotlib backend is used when running in a Web Worker (see the open issue as of the creation of this project)

If running in a regular Python environment, the drawing is displayed using the default Matplotlib backend.

worker.js

1. Import Pyodide
2. Initialize Pyodide
3. Load packages
4. Import the Python code as a module
5. Render images at intervals

index.html

Provide a placeholder to display the data coming from the Worker event.

Running Python locally

From a shell:

# Create a Python virtual environment
python3 -m venv .venv
source .venv/bin/activate
pip install -r requirements.dev.txt
python plot.py

The javascript and html code can be tested after running python3 -m http.server and visiting http://localhost:8000.