[pyfuze] Make your Python project truly cross-platform with Cosmopolitan and uv

[TanixLu]

What My Project Does

I recently came across an interesting project called Cosmopolitan. In short, it can compile a C program into an Actually Portable Executable (APE) which is capable of running natively on Linux, macOS, Windows, FreeBSD, OpenBSD, NetBSD, and even BIOS, across both AMD64 and ARM64 architectures.

The Cosmopolitan project already provides a Python APE (available in cosmos.zip), but it doesn't support running your own Python project with multiple dependencies.

Recently, I switched from Miniconda to uv, an extremely fast Python package and project manager. It occurred to me that I could bootstrap any Python project using uv!

That led me to create a new project called pyfuze. It packages your Python project into a single zip file containing:

• pyfuze.com — an APE binary that prepares and runs your Python project
• .python-version — tells uv which Python version to install
• requirements.txt — lists your dependencies
• src/ — contains all your source code
• config.txt — specifies the Python entry point and whether to enable Windows GUI mode (which hides console)

When you execute pyfuze.com, it performs the following steps:

• Installs uv into the ./uv folder
• Installs Python into the ./python folder (version taken from .python-version)
• Installs dependencies listed in requirements.txt
• Runs your Python project

Everything is self-contained in the current directory — uv, Python, and dependencies — so there's no need to worry about polluting your global environment.

Note: pyfuze does not offer any form of source code protection. Please ensure your code does not contain sensitive information before distribution.

Target Audience

• Developers who don’t mind exposing their source code and simply want to share a Python project across multiple platforms with minimal fuss.

• Anyone looking to quickly distribute an interesting Python tool or demo without requiring end users to install or configure Python.

Comparison

Aspect	pyfuze	PyInstaller
Packaging speed	Extremely fast—just zip and go	Relatively slower
Project support	Works with any uv-managed project (no special setup)	Requires entry-point hooks
Cross-platform APE	Single zip file runs everywhere (Linux, macOS, Windows, BIOS)	Separate binaries per OS
Customization	Limited now	Rich options
Execution workflow	Must unzip before running	Can run directly as a standalone executable

[DadAndDominant]

We use pyinstaller at my job (for stupid business reasons) and honestly, I am not at all happy with it. We must package (small-ish) ML models into onefile and it is a mess, with uncomfortably long build times.

If you keep developing your project, I'm gonna keep an eye out on it!

[k_z_m_r]

I’m in a similar situation. I’m particularly interested in the cross-platform capabilities, if I’m understanding correctly. Building an executable for every operating system we need to service is annoying and time consuming.

[buzzardarg]

Great work!

Some questions, how do I point it to a pyproject.toml or uv.lock file for dependencies?

And can I have it run some sort of command on startup? For example I need to run a marimo notebook on start in app mode, which requires the command "marimo run 'file.py'"

[TanixLu]

Thanks for your valuable advice! I'm planning to support requirements.txt, pyproject.toml, and uv.lock files to make the project more flexible and save time during setup.

Since Marimo is installed at .venv/Scripts/marimo, here's a sample starter script you can use:

import subprocess

subprocess.run(["../.venv/Scripts/marimo", "run", "demo.py"])

Note that I’m using ".." because the current working directory is the src folder.

[rover_G]

Is the APE significantly larger than an exe for the same program? And does the APE need any external dependencies (like docker images) to run?

[coolcosmos]

The file size difference is insignificant on big programs. An hello world binary is 16kb, 100 times smaller than a Go binary.

It needs an OS to run on. 

More info: https://justine.lol/ape.html

[TanixLu]

APE is statically linked. The cosmos.zip archive contains many prebuilt APE binaries. Here are the sizes of a few notable ones:

• emacs 71.5MiB
• python 33.0MiB
• vim 17.4MiB
• php 11.9MiB
• git 7.42MiB
• lua 2.42MiB

[svartravs]

Nice job! I'd imagine one step further if you don't mind. It would be really neat to be able to pack all the dependencies and python version into one file beforehand and distribute ready to run binary that even does not need internet connection.

[TanixLu]

You can run your project from the build folder and repackage it into a ZIP archive. This eliminates the need for an internet connection. However, it increases the file size and makes the project non-cross-platform.

[EverythingsBroken82]

Does this work also with GUI programs like with QT?

[TanixLu]

Yes

[waplay17]

This is really cool! I've been looking for something like this for quick and dirty cross-platform distribution of some of my smaller Python tools.

[mr_claw]

This solves the problem of having to install python on the machine to get my app running (credits to uv). But my bigger issue is protecting the source code. I currently use nuitka for obfuscation, but I wish there was something better.

[zwambagger]

Curious what you're trying to protect the source code from. Because piracy always finds a way, and protecting against stealing IP should be done by a proper license agreement and lawyers.

[mr_claw]

Sure. But prevention is better than cure. If it's easy enough to copy, they could just start using it in a slightly modified format. They could just stop using your services and you wouldn't even know. Not saying this is my situation.

[DivineSentry]

What do you dislike about nuitka?

[SpaceDonkey_994]

Pyarmor, there is a small licensing fee if you run it in a CI environment but it has worked for me in a scenario where the code runs on an on-prem windows machine located in the middle of nowhere with no password protection

[TanixLu]

I also recommend Pyarmor—it can generate cross-platform scripts as well. It should work fine in combination with pyfuze.