https://live.sympy.org/

It's basically an interactive Python session using a Python interpreter compiled to WebAssembly and which then runs locally on your device via your browser without having to install anything on your end.

It's very cool to check some calculation out very quickly on your phone or tablet.

Or if you want a full local Jupyterlab experience using the same WebAssembly tech: https://jupyterlite.readthedocs.io/en/stable/_static/lab/index.html (based on the JupyterLite project: https://github.com/jupyterlite/jupyterlite)