PySide6 + Nuitka is very impressive (some numbers and feedback inside)

Posted by setwindowtext@reddit | Python | View on Reddit | 34 comments

In preparation for releasing a new version of Flowkeeper I decided to try replacing PyInstaller with Nuitka. My main complaint about PyInstaller was that I could never make it work with MS Defender, but that's a topic for another time.

I've never complained about the size of the binaries that PyInstaller generated. Given that it had to bundle Python 3 and Qt 6, \~100MB looked reasonable. So you can imagine how surprised I was when instead of spitting out a usual 77MB for a standalone / portable Windows exe file it produced... a 39MB one! It is twice smaller, seemingly because Nuitka's genius C compiler / linker could shed unused Qt code so well.

Flowkeeper is a Qt Widgets app, and apart from typical QtCore, QtGui and QtWidgets it uses QtMultimedia, QtChart, QtNetwork, QtWebSockets and some other modules from PySide6_Addons. It also uses Fernet cryptography package, which in turn bundles hazmat. Finally, it includes a 10MB mp3 file, as well as \~2MB of images and fonts as resources. So all of that fits into a single self-contained 40MB exe file, which I find mighty impressive, especially if you start comparing it against Electron. Oh yes, and that's with the latest stable Python 3.13 and Qt 6.8.2.

I was so impressed, I decided to see how far I can push it. I chopped network, audio and graphing features from Flowkeeper, so that it only used PySide6_Essentials, and got rid of large binary resources like that mp3 file. As a result I got a fully functioning advanced Pomodoro timer with 90% of the "full" version features, in an under 22MB portable exe. When I run it, Task Manager only reports 40MB of RAM usage.

And best of all (why I wanted to try Nuitka in the first place) -- those exe files only get 3 false positives on VirusTotal, instead of 11 for PyInstaller. MS Defender and McAfee don't recognize my program as malware anymore. But I'll need to write a separate post for that.

Tl;dr -- Huge kudos to Nuitka team, which allows packaging non-trivial Python Qt6 applications in \~20MB Windows binaries. Beat that Electron!

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DivineSentry@reddit

I’m part of the Nuitka team, one of the largest reasons for the lower binary sizes is because we do a lot of debloating manually, I’m not sure the linker helps that much here actually. But I’m very happy that it worked so well for you :)

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noobposter123@reddit

I'm getting the opposite of the poster. If I use nuitka my stuff gets flagged as malware by 30+ AV. Whereas with pyinstaller just 1 flags it.

That said I'm using a nuitka that downloads mingw during the build.

So I'm not sure whether my nuitka generated exe is somehow compromised or not even though the py is 100% clean (not malware).

python -m nuitka --version
2.6.8
Commercial: None
Python: 3.12.9 (tags/v3.12.9:fdb8142, Feb  4 2025, 15:27:58) [MSC v.1942 64 bit (AMD64)]
Flavor: CPython Official
Executable: ~\AppData\Local\Programs\Python\Python312\python.exe
OS: Windows
Arch: x86_64
WindowsRelease: 10
Version C compiler: ~\AppData\Local\Nuitka\Nuitka\Cache\DOWNLO~1\gcc\x86_64\14.2.0posix-19.1.1-12.0.0-msvcrt-r2\mingw64\bin\gcc.exe (gcc 14.2.0).

python.exe SHA256: 805fd29612c221ebea570d372ec5ed46093c25a1033f1765de9b2f8103868886
winlibs-x86_64-posix-seh-gcc-14.2.0-llvm-19.1.1-mingw-w64msvcrt-12.0.0-r2.zip SHA256: d708da35e888c3c78732c006cbc8a5ab0ecb33f9a6f6e7105fd29fff56c642e8

Python312\Lib\site-packages\nuitka\utils\Download.py has:
def getCachedDownloadedMinGW64(target_arch, assume_yes_for_downloads, download_ok):
    # Large URLs, pylint: disable=line-too-long

    if target_arch == "x86_64":
        url = "https://github.com/brechtsanders/winlibs_mingw/releases/download/14.2.0posix-19.1.1-12.0.0-msvcrt-r2/winlibs-x86_64-posix-seh-gcc-14.2.0-llvm-19.1.1-mingw-w64msvcrt-12.0.0-r2.zip"
        binary = r"mingw64\bin\gcc.exe"
    elif target_arch == "x86":
        url = "https://github.com/brechtsanders/winlibs_mingw/releases/download/14.2.0posix-19.1.1-12.0.0-msvcrt-r2/winlibs-i686-posix-dwarf-gcc-14.2.0-llvm-19.1.1-mingw-w64msvcrt-12.0.0-r2.zip"
        binary = r"mingw32\bin\gcc.exe"

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DivineSentry@reddit

what does your program do?

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noobposter123@reddit

It uses pandas and openpyxl and compares certain excel files and optionally generates an excel file with the results. Libs used:

import os
import pandas as pd
from pathlib import Path
import argparse
import sys
from openpyxl import load_workbook

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DivineSentry@reddit

feel free to message me on discord `.krrt`

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noobposter123@reddit

VirusTotal results for the datetime py:

Nuitka: VirusTotal - File - c2669321e4773fe728d4c4377e80ceb2cae27f17413492f3f3612c7184b0c94d

Pyinstaller: VirusTotal - File - 82286909cfae08f2e4ec48f39604b8efa2d6852f9801c5f0be98f393f426a53d

FWIW both have this in the behavior Highlighted Text:

"The program can't start because api-ms-win-core-path-l1-1-0.dll is missing from your computer. Try reinstalling the program to fix this problem. ".

Wonder if the AV sandbox is running Win 7 or similar...

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DivineSentry@reddit

that dll missing error happens typically when you build in a newer build of windows, i.e windows 11, and move the binary to an older version, windows 7, generally you want to build in the same OS version as the target distribution OS, with that being said, without seeing the source code I can't build it and try it out.

you can try building it via GHA and see if that helps

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noobposter123@reddit

For example the following py code gets 26 flags on virustotal when I use nuitka but 5 when using pyinstaller:

from datetime import datetime

# Get current date and time in ISO 8601 format
current_datetime = datetime.now().isoformat()
print(current_datetime)

However some of my pyinstaller bundled exes can't remove the temp dir on some systems - probably interaction with AV/DLP/etc scans that cause some dlls to be locked (e.g. VCRUNTIME140.dll).

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setwindowtext@reddit (OP)

Great job either way, thanks for your work! When I saw it generates C code and then compiles it, I immediately thought -- "that's the way!"

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Lagulous@reddit

Appreciate all the work your team puts into making this possible. It's seriously a game-changer for Python desktop apps.

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dataguzzler@reddit

Nuitka is great, I made a simple GUI for it a while back https://github.com/non-npc/Py-Nuitka-GUI

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Peter3571@reddit

Gave it a quick try, it got stuck on the Y/N input question.

Is it OK to download and put it in 'C:\Users\Peter\AppData\Local\Nuitka\Nuitka\Cache\DOWNLO~1\gcc\x86_64\14.2.0posix-19.1.1-12.0.0-msvcrt-r2'.

When running normally, the next line is:

Fully automatic, cached. Proceed and download? [Yes]/No :

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dataguzzler@reddit

from the readme.md: Some options may have additional dependencies that must be installed by Noitka before use. In this case, in the Compiler output you would see that Noitka is asking to install for example 'dependencywalker', when this happens click the "Display Commands" button in Py Noitka GUI and run that in your console. Then you will see the option to install the modules that Noitka is requesting to install. Click (Y) and once the installation is done, you should be able to use Py Noitka GUI without any issues.

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dataguzzler@reddit

yes once you get past that the first time, it should run fine

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DaelonSuzuka@reddit

I'd be interested in reading more about your conversion. I have several PySide6 applications that currently use PyInstaller and it's sort of fine, but this sounds like a worthwhile upgrade.

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setwindowtext@reddit (OP)

Well, there's not much to say about the conversion itself -- using Nuitka is actually much easier compared to PyInstaller, it took me less trial-and-error to figure out correct parameters. Of course, this is also because I've already had all the inputs for PyInstaller, most of which I could just straight copy-paste to Nuitka.

Here's how I use Nuitka for Flowkeeper in GitHub pipeline: https://github.com/flowkeeper-org/fk-desktop/blob/cf1604ce4e2b6d8dfa4531d35fbcc1576def7ec1/.github/workflows/build.yml#L77

And here's an example of executing it on my development machine to build a DMG for macOS: https://github.com/flowkeeper-org/fk-desktop/blob/rc-0.10.0/scripts/macos/package-nuitka.sh

Here are the corresponding PyInstaller specs for comparison: https://github.com/flowkeeper-org/fk-desktop/tree/rc-0.10.0/scripts/common/pyinstaller

This is still work in progress, but should give an idea.

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DaelonSuzuka@reddit

Thanks! I'll probably try it out this weekend.

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m02ph3u5@reddit

I'm always impressed by Nuitka and the creator also seems to be a cool and very responsive dude. Bug reports always got fixed in an instant.

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bjorneylol@reddit

If you are distributing Pyinstaller applications you need to build your own bootloader to avoid virus false positives. If you ship the .exe that comes with the pypi package you are shipping a program that has been bundled in hundreds of known malware releases already

https://pyinstaller.org/en/stable/bootloader-building.html

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VovaViliReddit@reddit

Oh wow, TIL.

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setwindowtext@reddit (OP)

Interesting, I didn't know that. So the main purpose of building that bootloader yourself is to not have the same antivirus signatures? Sounds crazy that you have to go through all this hassle just to fool the AV :(

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bjorneylol@reddit

It's there in case you want to customize the bootloader or distribute it on an unsupported OS, but yes, it also generates a new signature

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Numerlor@reddit

my last release with pyside networking and audio on pyinstaller was 27 MB, just have to manually chop off DLLs before building.

It was 17MB a while back but more DLLs became mandatory with newer releases with the app not launching without them

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setwindowtext@reddit (OP)

I tried chopping DLLs off my PyInstaller build directory -- it worked to a certain extent. I could never bring it down to half the size like Nuitka does, and was always worrying that I'm gonna remove something important and my app won't work on some rare Linux DE, for example. At the end of the day I decided to play it safe.

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Numerlor@reddit

I guess one could look at how nuitka removes stuff as at the end it can still only remove the shared binaries if you're not configuring the whole Qt build system. But I'm not worried about linux as I only have windows builds so certainly simpler to verify it's working

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setwindowtext@reddit (OP)

For me Linux packaging creates more problems than Windows and macOS combined, mainly because Linux desktop cares less about compatibility. One would naively assume that building on an older OS like Ubuntu 20.04 would make your binary compatible with the widest range of systems, but in practice that's not the case due to stuff like "Wayland introduced a breaking change in 2022, so your Qt application now crashes with some obscure unresolved runtime linking error on 24.04".

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fenghuangshan@reddit

i downloaded the exe from your website , it's over 70MB. is the new small-size version not released yet?

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setwindowtext@reddit (OP)

I haven't published it yet, just wanted to share some quick findings. I'm currently finishing the GitHub build pipeline, which does a matrix build of [windows-x86, windows-arm, linux-x86, linux-arm, macOS-x86, macOS-arm] x [nuitka, pyinstaller] -- when it is done I'll use it to build the new release, which is otherwise ready.

Here's some details: https://www.reddit.com/r/Python/comments/1je94cf/comment/mil45a4/?utm_source=share&utm_medium=web3x&utm_name=web3xcss&utm_term=1&utm_content=share_button

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chat-lu@reddit

Do you get this with the free version or do you need the commercial one?

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setwindowtext@reddit (OP)

It work with the free version for me.

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DivineSentry@reddit

With the free version, most people don’t need the commercial version (Nuitka)

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m4xxp0wer@reddit

I should check it out again.
The last time i used it, my results were like 400MB with Nuitka vs 85MB with PyInstaller. And ~10 times longer build time.

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setwindowtext@reddit (OP)

I build both Nuitka and PyInstaller binaries. In my case build times compare as following:

Nuitka: Windows -- 5:51, macOS -- 6:24
PyInstaller: Windows -- 1:09, macOS -- 0:32

So yes, Nuitka is 5 -- 10 times slower than PyInstaller, and probably consumes way more RAM. Little wonder, given that it has to generate C code, compile it, link and then compress the resulting binaries.

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DivineSentry@reddit

The reason for the longer build time is that Nuitka actually transpiles as much code as it can to C / C++ and as such that code needs to be compiled, pyinstaller simply just bundles everything into a single archive (think similarly to a zip) and then converts that into an exe, very different techniques