python-for-android provides several major choices for build components. This page describes the advantages and drawbacks, and extra technical details or requirements, in each case.

python-for-android now supports building APKs with either python2 or python3, but these have extra requirements or potential disadvantages as below.

Select this by adding it in your requirements, e.g. --requirements=python2.

This option builds Python 2.7.2 for your selected Android architecture, and includes it in the APK. There are no special requirements, all the building is done locally.

The python2 build is also the way python-for-android originally worked, even in the old toolchain.

Select this by adding the python3crystax recipe to your requirements, e.g. --requirements=python3crystax.

This uses the prebuilt Python from the CrystaX NDK, a drop-in replacement for Google's official NDK which includes many improvements. As such, you must use the CrystaX NDK 10.3.0 or higher when building with python3. You can get it here.

python3 inclusion should work fine, including all existing recipes, but internally this is handled quite differently to the locally built python2 so there may be bugs or surprising behaviours. If you come across any, feel free to open an issue.

The experimental status also means that some features are missing and the build is not fully optimised so APKs are probably a little larger and slower than they need to be. This is currently being addressed, though it's not clear how the final result will compare to python2.

python-for-android supports multiple bootstraps, the Java and JNI code that starts the app and the python interpreter, then handles interactions with the Android OS.

Currently the following bootstraps are supported, but we hope that it it should be easy to add others if your project has different requirements. Let us know if there are any improvements that would help here.

You can use this with --bootstrap=sdl2, or simply include the sdl2 recipe in your --requirements.

SDL2 is a popular cross-platform depelopment library, particularly for games. It has its own Android project support, which python-for-android uses as a bootstrap, and to which it adds the Python build and JNI code to start it.

From the point of view of a Python program, SDL2 should behave as normal. For instance, you can build apps with Kivy, Vispy, or PySDL2 and have them work with this bootstrap. It should also be possible to use e.g. pygame_sdl2, but this would need a build recipe and doesn't yet have one.

You can use this with --bootstrap=webview, or simply include the webviewjni recipe in your --requirements.

The webview bootstrap gui is, per the name, a WebView displaying a webpage, but this page is hosted on the device via a Python webserver. For instance, your Python code can start a Flask application, and your app will display and allow the user to navigate this website.

This bootstrap will automatically try to load a website on port 5000 (the default for Flask), or you can specify a different option with the --port command line option. If the webserver is not immediately present (e.g. during the short Python loading time when first started), it will instead display a loading screen until the server is ready.

You can use this with --bootstrap=pygame, or simply include the pygame recipe in your --requirements.

The pygame bootstrap is the original backend used by Kivy, and still works fine for use with Kivy apps. It may also work for pure pygame apps, but hasn't been developed with this in mind.

This bootstrap will eventually be deprecated in favour of sdl2, but not before the sdl2 bootstrap includes all the features that would be lost.