pythonista3:

pythonista: URL scheme

[1] The Pythonista URL Scheme — Pythonista Documentation () <http://omz-software.com/pythonista/docs/ios/urlscheme.html>

In Pythonista 3.x, you can use pythonista3:// instead of pythonista://. In Pythonista 2 (starting with 2.1), you can use pythonista2://. Use these schemes if you want to target a specific version of the app. In case both apps are installed, it is undefined which one of them handles a pythonista:// URL.