Build serious-python with Python 3.13 for Cython mobile support

[EH-MLS]

Feature Request

We would like to build serious-python with Python 3.13, instead of Python 3.12, to enable cythonizing Python modules for use in mobile deployments.

Currently, Python 3.12 does not seem to support or allow cythonizing Python modules for mobile deployments as required. If there is any recommended or alternative approach that allows cythonizing Python modules for mobile using Python 3.12, please document or provide guidance for that as well.

Linked Discussion

Original request and context: flet-dev/flet#6077

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Ideal Solution:

• Official support for building serious-python (and ultimately Flet/Flutter bundles) with Python 3.13.
• Support for using Cython-based Python modules on mobile platforms via serious-python.

Alternatives:

• Guidance or documentation on making this work with Python 3.12 if possible.

Thank you!

[EH-MLS]

Summary: What it takes to ship serious-python with Python 3.13

After analyzing the serious-python codebase, here's a breakdown of all the changes required to migrate from Python 3.12 to 3.13.

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0. 🔑 Prerequisite: Build Python 3.13 Distributions (flet-dev/python-build)

Before anything in serious-python can change, new prebuilt Python 3.13 runtime distributions must be built and published via flet-dev/python-build. These are the platform archives that serious-python downloads at build time:

• python-android-dart-3.13-{abi}.tar.gz (arm64-v8a, armeabi-v7a, x86_64, x86)
• python-ios-dart-3.13.tar.gz
• python-macos-dart-3.13.tar.gz
• python-linux-dart-3.13-{arch}.tar.gz
• python-windows-for-dart-3.13.zip

This is the biggest prerequisite — cross-compiling CPython 3.13 for iOS and Android.

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1. 📦 Packaging CLI (package_command.dart)

Update the central version constants:

// src/serious_python/bin/package_command.dart (line 21-22)
const buildPythonVersion = "3.12.9";       // → "3.13.x"
const buildPythonReleaseDate = "20250205"; // → new release date

These control which Python is downloaded from astral-sh/python-build-standalone for the host-side packaging step (running pip to install dependencies).

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2. 🤖 Android

build.gradle

// src/serious_python_android/android/build.gradle (line 4)
def python_version = '3.12'  // → '3.13'

Controls the download URL for Android native Python distributions.

serious_python_android.dart

// src/serious_python_android/lib/serious_python_android.dart (line 97)
return runPythonProgramFFI(sync ?? false, "libpython3.12.so", appPath, script ?? "");
// → "libpython3.13.so"

python_ffigen.yaml

# src/serious_python_android/python_ffigen.yaml (lines 16-21)
# All python-3.12 / python3.12 header paths → python-3.13 / python3.13
# Then re-run: dart run ffigen --config python_ffigen.yaml
# to regenerate lib/src/gen.dart

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3. 🍎 Darwin (iOS + macOS)

serious_python_darwin.podspec

# src/serious_python_darwin/darwin/serious_python_darwin.podspec (line 31)
python_version = "3.12"  # → "3.13"

This version is passed to prepare_ios.sh and prepare_macos.sh, which download python-ios-dart-{version}.tar.gz and python-macos-dart-{version}.tar.gz.

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4. 🐧 Linux

CMakeLists.txt

# src/serious_python_linux/linux/CMakeLists.txt
set(PYTHON_VERSION "3.12")                                     # → "3.13"
include_directories("${PYTHON_PACKAGE}/include/python3.12")    # → python3.13
# libpython3.12.so.1.0 → libpython3.13.so.1.0
# lib/python3.12 → lib/python3.13

serious_python_linux_plugin.cc

// src/serious_python_linux/linux/serious_python_linux_plugin.cc (line 102)
module_paths_str_array[i++] = g_strdup_printf("%s/python3.12", exe_dir);
// → "python3.13"

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5. 🪟 Windows

CMakeLists.txt

# src/serious_python_windows/windows/CMakeLists.txt
set(PYTHON_URL ".../v3.12/python-windows-for-dart-3.12.zip")   # → v3.13 / 3.13
# python312.lib → python313.lib
# python312.dll → python313.dll

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6. 📄 Documentation

# src/serious_python/README.md (line 25)
* Python 3.12.6 on all platforms.
<!-- → Python 3.13.x on all platforms. -->

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⚠️ CPython C API Compatibility

Python 3.13 introduced C API changes, including removal of some deprecated APIs and the new experimental free-threaded build mode. After updating the header paths:

1. Regenerate FFI bindings (dart run ffigen) against Python 3.13 headers
2. Review generated gen.dart for any breaking changes
3. Verify native C code (serious_python.c, platform plugins) against removed/changed APIs

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✅ Checklist

#	Area	File(s)	Change
0	Upstream (blocker)	flet-dev/python-build CI	Build & publish Python 3.13 distros for all platforms
1	Packaging CLI	package_command.dart	buildPythonVersion + buildPythonReleaseDate
2	Android Gradle	build.gradle	python_version = '3.13'
3	Android Dart FFI	serious_python_android.dart	libpython3.12.so → libpython3.13.so
4	Android FFI headers	python_ffigen.yaml + re-run ffigen	Header paths, regenerate gen.dart
5	iOS / macOS	serious_python_darwin.podspec	python_version = "3.13"
6	Linux CMake	CMakeLists.txt	Version, includes, .so names, stdlib paths
7	Linux C++ plugin	serious_python_linux_plugin.cc	Module path string
8	Windows CMake	CMakeLists.txt	URL, .lib / .dll names
9	Docs	README.md	Version string
10	C API compat	Generated bindings + native code	Verify against 3.13 API changes

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💡 Notes

• The blocking prerequisite is step 0 — everything else is essentially version string bumps + regenerating FFI bindings.
• Once python-build publishes 3.13 archives, the serious-python changes are relatively mechanical.
• The main risk area is CPython C API compatibility in the FFI layer and native plugin code.
• This would also unblock Cython support for mobile, since cibuildwheel supports iOS/Android targets only on Python 3.13+.

[FeodorFitsner]

It's bigger than that.

First, there is https://github.com/flet-dev/python-build building/re-packaging Python runtime itself for all 5 platforms. For Python 3.13/3.14 we would need to switch to iOS/Android runtimes built into Pythons.

Second, there is https://github.com/flet-dev/mobile-forge/tree/python3.12/recipes building binary packages for Python 3.12 hosted at https://pypi.flet.dev/. The recipes must be adjusted for newer versions of their packages and Python 3.13.

[FeodorFitsner]

Adding 3.13 support to serious_python package itself is a trivial task for an AI agent (as you see by asking it to analyze and do a plan).

[FeodorFitsner]

Anyway, we started working on 3.13/3.14 support 🚧

[EH-MLS]

thanks!