flet build macos with numpy - built app crashes

[tokyohandsome]

Description Building Flet app with numpy completes with no error on mac, but built app crashes right after opening a window.

Code example to reproduce the issue:

import flet as ft
import numpy as np

def main(page: ft.Page):
    page.add(
        ft.Text(f'Value: {np.random.random_sample()}')
        )

ft.app(target=main)

Build command:

flet build macos

Describe the results you received:

Built app crashes right after rendering a window. Running the app by python main.py or flet run main.py works fine. After commenting import numpy as np out, built app renders a window with no content. It won't crash.

Describe the results you expected:

Random float something like Value: 0.8875341508950007 appears on a window.

Additional information you deem important (e.g. issue happens only occasionally):

App built by flet pack main.py won't crash and works as expected.

Flet version (pip show flet):

Name: flet
Version: 0.21.2
Summary: Flet for Python - easily build interactive multi-platform apps in Python
Home-page: 
Author: Appveyor Systems Inc.
Author-email: [email protected]
License: Apache-2.0
Location: /Users/handsome/Documents/Python/fletAudioPlayback/.venv/lib/python3.11/site-packages
Requires: cookiecutter, fastapi, flet-runtime, packaging, qrcode, uvicorn, watchdog
Required-by: 

Give your requirements.txt file (don't pip freeze, instead give direct packages):

numpy

Operating system:

ProductName: macOS ProductVersion: 14.3.1 BuildVersion: 23D60

M2 Max 12 core CPU + 30 core GPU 32GB RAM

Additional environment details:

% python --version
Python 3.11.7

% pip list|grep numpy
numpy                     1.26.4

% flutter --version
Flutter 3.19.3 • channel stable • https://github.com/flutter/flutter.git
Framework • revision ba39319843 (2 weeks ago) • 2024-03-07 15:22:21 -0600
Engine • revision 2e4ba9c6fb
Tools • Dart 3.3.1 • DevTools 2.31.1

% brew list cocoapods
Warning: Treating cocoapods as a formula. For the cask, use homebrew/cask/cocoapods or specify the `--cask` flag.
/opt/homebrew/Cellar/cocoapods/1.15.2/bin/pod
/opt/homebrew/Cellar/cocoapods/1.15.2/bin/xcodeproj
/opt/homebrew/Cellar/cocoapods/1.15.2/libexec/bin/ (5 files)
/opt/homebrew/Cellar/cocoapods/1.15.2/libexec/cache/ (34 files)
/opt/homebrew/Cellar/cocoapods/1.15.2/libexec/doc/ (11485 files)
/opt/homebrew/Cellar/cocoapods/1.15.2/libexec/extensions/ (4 files)
/opt/homebrew/Cellar/cocoapods/1.15.2/libexec/gems/ (2166 files)
/opt/homebrew/Cellar/cocoapods/1.15.2/libexec/specifications/ (34 files)

% xcodebuild -version 
Xcode 15.3
Build version 15E204a

[torablien]

I can reproduce this issue by simply adding the numpy import to a hello world file.

Works:

import flet as ft


def main(page: ft.Page):
    page.add(ft.Text("Hello World!"))


ft.app(main)

Fails with crash after build:

import flet as ft
import numpy as np


def main(page: ft.Page):
    page.add(ft.Text("Hello World!"))


ft.app(main)

As the reporter noted, this causes a crash, after which point, all apps in this project will render a blank page (no crash), even if you remove the dependency.

The app works with flet run and even flet pack suggesting there may be an issue with flet build.

[FeodorFitsner]

Related: https://github.com/flet-dev/serious-python/issues/85

[FeodorFitsner]

There is an explanation and workaround for "numpy on macos" issue: https://github.com/flet-dev/serious-python/issues/85#issuecomment-2065000974

Either re-build the app with flet build macos (both 0.21.2 and 0.22.0 build templates where updated to set OPENBLAS_NUM_THREADS variable or implement a fix in your own python app.

[tokyohandsome]

Great! Thank you, @FeodorFitsner ! I just tested building my app with 0.21.1 and 0.22.0 without modifying my code, and both built apps worked with no issue. Awesome!