[FIXED] How to ignore root warnings?

Issue

I generate monochromatic images and save them using imageio.imwrite. Every time I save a file I get a following warning:

WARNING:root:Lossy conversion from float64 to uint8. Range [-0.24890179009891278, 2.35786261304524]. Convert image to uint8 prior to saving to suppress this warning.

I don't care for this "lossy conversion". Everything looks well and works fine.

However, every ~100 generated images I got different warning which I want to catch. Thus I want to ignore the above one.

I tried to ignore it, but even if I call

import warnings
warnings.simplefilter('ignore')

beforehand I still get this warning.

Solution

The library doesn't use the warnings module. Instead, it logs a message using the logging framework, by calling the top-level logging.warning() function. See the imageio.core.util._precision_warn() function:

from logging import warning as warn

# ...

def _precision_warn(p1, p2, extra=""):
    t = (
        "Lossy conversion from {} to {}. {} Convert image to {} prior to "
        "saving to suppress this warning."
    )
    warn(t.format(p1, p2, extra, p2))

This is... unfortunate, as you can't easily disable this using the logging API. Best practice is to use a dedicated named logger for libraries.

As such, it is probably best to patch the library no make the above function a no-op:

import imageio.core.util

def silence_imageio_warning(*args, **kwargs):
    pass

imageio.core.util._precision_warn = silence_imageio_warning

You could also silence all logging, adjusting configurion on the root logger. This is not ideal, as you may want to use logging yourself or use third-party libraries that are better behaved.

I've filed an issue with the project to ask them to fix their logging story.

Answered By - Martijn Pieters

Answer Checked By - Pedro (PHPFixing Volunteer)