How to Disable Warnings in Python

Introduction

Working with any language, you've probably come across warnings - and lots of them. In Python, our warnings are the yellow-highlighted messages that appear when code runs. These warnings are Python's way of telling us that, while our code is technically correct and will run, there's something in it that's not quite right or could eventually lead to issues. Sometimes these warnings are helpful, and sometimes they're not. So what if we want to disable them?

In this Byte, we'll show a bit more about what Python warnings are, why you might want to disable them, and how you can do it.

Python Warnings

Python warnings are messages that the Python interpreter throws when it encounters unusual code that may not necessarily result in an error, but is probably not what you intended. These warnings can include things like deprecation warnings, which tell you when a Python feature is being phased out, or syntax warnings, which alert you to weird but syntactically correct code.

Here's an example of a warning you might see:

import warnings

def fxn():
    warnings.warn("fxn() is deprecated", DeprecationWarning, stacklevel=2)

warnings.simplefilter('always', DeprecationWarning)
fxn()

When you run this code, Python will output a DeprecationWarning:

$ python warnings.py 
warnings.py:9: DeprecationWarning: fxn() is deprecated
  fxn()

Note: We had to add the warnings.simplefilter('always', DeprecationWarning) line in order to get the warning to show. Otherwise DeprecationWarnings are ignored by default.

Why disable them?

That's a good question. Warnings are indeed useful, but there are times when you might want to disable them.

For example, if you're working with a large codebase and you're aware of the warnings but have decided to ignore them for now, having them constantly pop up can be not only annoying but also cause you to miss more important output from your code. In the same vein, if you're running a script that's outputting to a log file, you might not want warnings cluttering up your logs.

How to Disable Python Warnings

There are a few ways to disable warnings in Python, and we'll look at three of them: using the warnings module, using command line options, and using environment variables.

Using the warnings Module

Python's warnings module provides a way to control how warnings are displayed. You can use the filterwarnings function to ignore all warnings programmatically:

import warnings
warnings.filterwarnings("ignore")

This will suppress all warnings. If you want to suppress only a specific type of warning, you can do so by specifying the warning class:

warnings.filterwarnings("ignore", category=DeprecationWarning)

In this case, only DeprecationWarnings will be suppressed.

Using Command Line Options

If you're running your Python script from the command line, you can use the -W option followed by ignore to suppress all warnings:

$ python -W ignore your_script.py

Using Environment Variables

You can also use the PYTHONWARNINGS environment variable to control the display of warnings. To ignore all warnings, you can set this variable to ignore:

$ export PYTHONWARNINGS="ignore"
$ python your_script.py

This will suppress all warnings for the entire session. If you want to suppress warnings for all sessions, you can add the export PYTHONWARNINGS="ignore" line to your shell's startup file (like .bashrc or .bash_profile for bash) so that this setting is always set.

Risks of Disabling Warnings

While there are several ways to disable warnings in Python, you should also understand the risks associated with doing this.

For example, a DeprecationWarning alerts you that a function you're using is slated for removal in a future version of Python or a library. If you ignore this warning, your code may suddenly stop working when you upgrade to a new version.

As a general rule, it's best to just fix the issues causing the warnings, instead of simply suppressing the warnings. There are, however, situations where removing warnings is actually the most practical solution, like when you're using a library that generates warnings you can't control and aren't actually helpful. In these cases, it's best to just suppress only the specific warnings you need to, and avoid using a blanket "ignore all" command.

Conclusion

Warnings are there for a reason, like signaling potential issues in the code that might lead to bugs or unexpected behavior, so it's best not to suppress them. However, there are times when you may want to disable these warnings, whether to clean up your console output or because you're aware of the warning and have decided it's not relevant to your particular situation.

In this Byte, we've learned about Python's warnings, how to suppress them, along with the potential risks of doing so.