EC
FutureWarning
PythonWARNINGCommonWarning

Behaviour will change in a future Python release

Quick Answer

Treat FutureWarning as a migration task — update the code before the next major Python release removes or changes the behaviour.

Production Risk

Low.

What this means

Indicates that a construct or API will change semantics in a future release. Visible to end users (unlike DeprecationWarning which targets developers). Address before upgrading Python.

Why it happens
  1. 1Using a regex flag combination that will change meaning in a future version
  2. 2A library API whose default argument value is being deprecated

Fix

Update to the new API before the version that changes it

Update to the new API before the version that changes it
import warnings
warnings.filterwarnings('error', category=FutureWarning)
# Run your tests — failures reveal every call site that needs updating

Why this works

Promoting FutureWarning to an error in tests forces all affected call sites to be fixed before deployment.

Code examples
Catch in test suitepython
import pytest
@pytest.mark.filterwarnings('error::FutureWarning')
def test_no_future_warnings():
    call_my_api()
Sources

Content generated with AI assistance and reviewed for accuracy. Found an error? hello@errcodes.dev

← All Python errors