How Python runs here
Python executes through Pyodide 0.28.3, a build of CPython for WebAssembly. The runtime is about 12 MB, served from this site rather than a third-party CDN, and loaded only after you click “Load Python and run”. It runs in a Worker inside a sandboxed frame, so Stop always works.
The standard library is available (dataclasses, collections, statistics, json, re, datetime and more). Each run starts with fresh globals.
What does not work
There is no pip, no network sockets, no threads or subprocesses, and input() is disabled. Packages such as NumPy are not bundled in this build. Python formatting (black) is not available. These limits are shown next to the Run button so nothing is promised that cannot happen.
How to use it
- Press Run and accept the one-time runtime download.
- Read the output in the Console tab.
- Change the readings list and run again; later runs start instantly.
Questions
Which Python version is it?
CPython 3.13 as packaged by Pyodide 0.28.3.
Can I install packages with pip?
No. Package installation would need network access and is outside this browser-only build. Use the standard library.
Why is the first run slow?
The interpreter (about 12 MB) is downloaded and compiled once. Your browser caches it, so later runs start in well under a second.