How to watch my builded flet app logs?

[ShibainuHacker]

Question

I am currently building a video conversion app using Flet. Internally, I am using a Python module that calls ffmpeg.

The app works perfectly when I run it with flet run, but after building it with flet build macos and running the generated app, it seems to encounter an error and does not function properly.

I would like to check the logs (such as print statements) from the code, but is there a way to view the logs of the app after it has been built?

Code sample

No response

Error message

No response

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• I have searched for answers to my question both in the issues and in previous discussions.

[tanmay-bhatgare]

you can use flet build apk -vv for detailed output in ternimal.

[ap4499]

I also encountered this problem, when I built my app (Flet Build), it was simply blank, or at times - froze.

Have a look at how to setup the Python logging function (basic example below), it will output to a text file (if setup to do so), and you can use it just as you would print statements in the terminal. You are going to need to insert a lot of logging code to isolate the issues and why it is that your program doesn't work correctly. Some of mine were in my actual code, but a lot of them were imports that were failing.

You haven't said what isn't working properly, but when I built on macos, binaries and runtime compiled elements from Torch were not being properly packaged by serious_python. I would suspect something as sophisticated as ffmpeg is encountering similar issues given it's a C library.

In the second code snippet, is how I found the libraries that were not being correctly imported - by wrapping them in a try loop, and logging the exceptions.

import logging
logger = logging.getLogger(__name__)
logger.setLevel(logging.DEBUG) 
logger.debug("Starting log.")

try:
    logger.debug("Importing: torch")
    import torch

except ImportError as e:
    logger.error(f"Import failed: {e}")

Using the above, I was able to see where the imports stopped working, and which lines of my code weren't working.

[tanmay-bhatgare]

Is torch a pure python library? Can it be converted into android wheel? I think this might cause error or blank screen.

[ap4499]

This was Torch for Windows/MacOS. I've already debugged + resolved. The OP question was for macos too.

The issue with dumping the binaries has already been flagged to Flet devs - an upcoming release should have an option to alter this behaviour.

Torch can be built for Android.. but it is complex, and not without limitations. You would likely be looking at inference only and ExecuTorch.

If you really.. really.. wanted to build PyTorch for Android, you can build your own wheels from source. But given the limited processing power of mobile devices, the absence of active cooling.. I'd question why.. you'd be better off with inference + cloud training.