I thought I’d write some short details about the actual history of
Python on Android from my own perspective. It’s something I’ve been
involved in on some level for about 8 years, and for a significant
part of that I’ve been a primary maintainer of python-for-android. This is a
build tool for creating APKs from Python applications, originally
created for Kivy but now more generic so
that it can also support e.g. flask running on the device with a
webview gui, or more recently Pygame via its upcoming SDL2 support.
Notes on the term "native"
A key problem point around discussing Python on Android in that the
term "native" is overloaded to mean two different things.
The first refers to simply compiling CPython to run "natively" with
the Android kernel and libraries, just as it does on desktop
platforms, and this is what the ZDNet article refers to with e.g. the
quote "Android devices are now fast enough, and the Android kernel
permissive enough, to run CPython itself". This is not a recent
development, it has been technically possible for many years, although
the article is correct that it comes with disadvantages and not
everything works the same as on desktop.
The second is using the "native" GUI toolkit for the platform. On
Android that means using the same widget toolkit as normal Java-based
development. This is the part that is difficult and not yet widely
supported, see below for more discussion about the recent
developments. I’m actually not sure if the ZDNet article intends to
focus on this, but perhaps fails because the author doesn’t understand
the distinction, certainly the article focuses on CPython technical details.
It’s absolutely true that having Python applications seamlessly
using the native GUI toolkit is essential to making Python a serious
alternative to Java for generic Android development. However, there
are huge areas of Python development where this simply isn’t a big
concern, e.g. everything from games (Pygame, Kivy, Renpy), to
scientific visualisation (matplotlib, Vispy, other toolkits), to
novel user interfaces (Jupyter notebooks or other apps that
don’t care about the native GUI toolkit for whatever reason). All of
these things are tremendously popular on the desktop without using the
native GUI toolkit, because that detail is either irrelevant or
specifically at odds with what they want to do.
History of Python for Android projects
The following projects are ones I remember as interesting and
historically important in terms of creating Python applications on
Android, in rough date order. This list undoubtedly isn’t complete and
is strongly based on events as I remember them, I might have missed
other important projects and I’m certainly missing details from before
about 2012! I’ve also focused on application build tools, not the many
individual patches and Python contributions that made them possible.
Pygame Subset for Android (PGS4A)
Pygame gained rudimentary Android support fairly early in Android’s
history. I’m not sure exactly what happened when, but this old
is from February 2011 and isn’t the first version.
PGS4A worked by compiling CPython for Android, with a modified version
of SDL (the gui library that Pygame uses), and some Java code to get
the app to start and display a surface that pygame could draw to. I
believe there were some limitations to what you could do (there’s a
reason it was a "subset" of Pygame), but I’m not sure what these were.
I remember people were actively using PGS4A around 2012 when I started
looking at it myself, but its popularity slowly diminished over time,
probably due to lack of developer support combined with its limitations.
Ren’Py is a visual novel engine with
great cross-platform support. Actually, I suspect it’s
quietly one of the most successful Python game engine projects,
e.g. you can find quite a few Renpy-made games available via Steam.
Renpy gained Android support a long time ago, maybe in 2011 or
earlier. I believe that as with PGS4A, it worked by combining pygame
with a modified version of SDL and some custom Java code to display an
app surface that Renpy could draw to. I’m not sure if the Renpy build
tools actually had history in common with PGS4A, but I don’t think
they were the same project at any point I remember.
Renpy’s Android support hasn’t been static, it’s evolved
since 2011. At some point around 2014-2015 it switched to use a fork
of Pygame using SDL2, with
corresponding updates to the Android build process. This makes sense
because SDL2 itself supports Android properly, removing a huge
maintenance burden. Note that this pygame_sdl2 project is not the same
as the SDL2 support currently under development from the core Pygame
team, I don’t think Renpy’s pygame_sdl2 is in wide use and I don’t
know what its limitations are.
Kivy and python-for-android
Kivy is easily the most well known
Android-supporting Python toolkit I’m aware of, and has been since
around 2012 when I came across it myself after failing to get a Java
Android tutorial working. Kivy is a graphical toolkit that was
not specifically designed for mobile support, but instead focused on
being generically cross-platform and supporting novel user
interfaces. This turned out very timely, as these properties made it
very well suited for Android and iOS support, although Kivy also
supports desktop use. Kivy draws its GUI using OpenGL, which
has the advantage of working essentially the same on all different
platforms, but this can also be a disadvantage in that it means not
using the native GUI toolkit as discussed above.
My understanding is that Kivy’s Android support was originally based
on Renpy’s Android build tools, which through some amount of
collaboration and changes from different places ended up being the
genesis for Kivy’s python-for-android project, first commit
November 2011. Renpy’s Android build project then shifted to use a
fork of python-for-android at some point, after which the projects
have been developed separately.
Python-for-android was originally quite Kivy-specific, but was totally
rewritten in 2015 to be a more generic and modular build tool,
coinciding with Kivy’s own transition to SDL2 as a default backend (in
fact this is where I really got involved). Since then its
breadth of support has increased dramatically.
BeeWare is a collection of tools and libraries for building Python
applications across different platforms, both desktop and
mobile. These projects have a particular focus on manipulating the
native graphical toolkits of a given platform, e.g. on Android they
want to use the same "native" GUI widgets as a normal Java-built
application. Its toga toolkit
provides a platform-independent GUI abstraction for this, in
combination with platform-specific toolkits for each individual target.
I believe the BeeWare developers (or at least the core developer
Russell Keith-Magee) did some initial experimentation using CPython on
Android somewhere around 2015. The idea there would be to create and
manipulate the normal Java-native GUI widgets using Java Native
Interface (JNI). This is actually possible, it’s something we also
support in Kivy and is occasionally useful to e.g. display a
webview. Unfortunately it has some key disadvantages including that
Python is still quite slow to start, and in particular that Android
used to enforce a fairly low limit on the number of JNI references
that could be simultaneously maintained, which makes building a full
GUI impractical. My understanding is that a combination of these
factors made CPython use impractical for Beeware on Android.
BeeWare instead switched to creating VOC, a Python code to Java bytecode
transpiler. This converts the Python input into genuine Java bytecode
that can run as a normal app without the above limitations. I haven’t
tried this for some time, but I understand it works fine. However, it
seems the difficulty of supporting the full breadth of Python
libraries has been a barrier (at least, that’s been my impression from
watching discussions about it, I think it’s still under active
development and working well).
Fortunately Android itself has improved, and in particular the
limitation on JNI references is no longer present in recent
versions. In 2019 BeeWare switched back to targeting CPython on
Android, supported by a PSF grant. It
is the outcome of this grant that led to the discussions and article I
linked at the top. See the end of this post for a brief summary.
Chaquopy provides build tools for
both including Python code in Java applications, and building apps
entirely in Python. I’m not sure about the technical details, but I’ve
been consistently aware of it as an active project since about 2017,
so it may be useful to anyone interested in this sort of thing. I
guess there must be some overlap with what python-for-android does,
but Chaquopy’s integration of Python and Java code seems to be more of
The popular Qt graphical framework supports Android. Python bindings to this
framework are quite popular, so it’s not a huge surprise that there’s
some level of Python for Android support using Qt for the GUI. As far
as I’m aware pyqtdeploy is
the primary build tool for this, using the PyQt bindings, but I may
not be up to date about it. I’ve never seen this to be very popular,
but I don’t know if there’s a reason for this beyond its relative obscurity.
What are actually the recent developments in CPython on Android?
Various contributors have driven improvements in CPython’s Android
support over the years. I would give more details but honestly I’ve
never found the time to get deeply involved so the historical summary
is limited by my own ignorance! This has brought CPython to the point
of being fairly easy to compile for Android as of about version 3.6.
For instance, python-for-android’s CPython build recipe applies no
essential patches to the Python 3 source, just an appropriate set of
The key recent development is the BeeWare project’s switch to CPython
explained above. They’ve made a specific goal of understanding where
CPython’s Android support can be improved, and getting involved to
resolve these problems. This means attacking both individual technical
issues (e.g. getting Python’s test suit passing correctly), and
longer-term structural problems (e.g. the suggestion described in the
ZDNet article to create a stripped-back Python kernel for mobile use).
These recent developments are great, and hopefully will lead to huge
improvements in the ease of deploying Python applications for Android,
especially addressing the missing functionality of using the native
Java GUI toolkit. However, let’s not forget the history of CPython on
Android, people have been creating applications for both business and
pleasure for many years.