Python 3 Android

This is an experimental set of build scripts that will cross-compile Python 3.9.0 for an Android device.

Prerequisites

Building requires:

1. Linux. This project might work on other systems supported by NDK but no guarantee.
2. Android NDK r21 installed and environment variable $ANDROID_NDK points to its root directory. Older NDK may not work and NDK <= r18 is known to be incompatible.
3. python3.9 binary from Python 3.9.0 on the building host. It's recommended to use exactly that Python version, which can be installed via pyenv. Don't forget to check that python3.9 is available in $PATH.
4. tic binary from ncurses 6.2 on the building host. Slightly newer or older version may also work but no guarantee.
5. A case-sensitive filesystem. The default filesystem on Windows and macOS is case-insensitive, and building may fail.

Running requires:

1. Android 5.0 (Lollipop, API 21) or above
2. arm, arm64, x86 or x86-64

Build

1. Run ./clean.sh for good measure.
2. For every API Level/architecture combination you wish to build for:
   • ARCH=arm ANDROID_API=21 ./build.sh to build everything!

Build using Docker/Podman

Download the latest NDK for Linux from https://developer.android.com/ndk/downloads and extract it.

docker run --rm -it -v $(pwd):/python3-android -v /path/to/android-ndk:/android-ndk:ro --env ARCH=arm --env ANDROID_API=21 python:3.9.0-slim /python3-android/docker-build.sh

Here /path/to/android-ndk should be replaced with the actual for NDK (e.g., /opt/android-ndk).

Podman is also supported. Simply replace docker with podman in the command above.

Installation

1. Make sure adb shell works fine
2. Copy all files in build to a folder on the device (e.g., /data/local/tmp/python3). Note that on most devices /sdcard is not on a POSIX-compliant filesystem, so the python binary will not run from there.
3. In adb shell:

cd /data/local/tmp/build
. ./env.sh
python3

And have fun!

SSL/TLS

SSL certificates have old and new naming schemes. Android uses the old scheme yet the latest OpenSSL uses the new one. If you got CERTIFICATE_VERIFY_FAILED when using SSL/TLS in Python, you need to collect system certificates: (thanks @GRRedWings for the idea)

cd /data/local/tmp/build
mkdir -p etc/ssl
cat /system/etc/security/cacerts/* > etc/ssl/cert.pem

Path for certificates may vary with device vendor and/or Android version. Note that this approach only collects system certificates. If you need to collect user-installed certificates, most likely root access on your Android device is needed.

Check SSL/TLS functionality with:

import urllib.request
print(urllib.request.urlopen('https://httpbin.org/ip').read().decode('ascii'))

Known Issues

No big issues! yay