This is an amazing Python framework just for this purpose: Kivy
I have personally developed using Kivy and I love it. It spans across multiple platforms ranging from Mac, Android, Linux etc.
Note: Native iOS development is possible but it is quite cumbersome to do so because Apple doesn't allow native scripting using anything apart from their language.
And, I think you will be aware of the Android Scripting Environment (ASE), right? Well, even if you don't - It is basically a tool to allow scripts to run on the Android environment.
For iOS Python development, all you have to do is you need to embed a Python interpreter into the application and later distribute the script with it.
Well, we do that last part so we can follow the rules/guidelines set by Apple.
Hope this helps, let me know if you need anything else. Cheers!