Example of context_aware_warnings behaviour

pool_warning_filter_example.py

# See: https://github.com/pytest-dev/pytest/issues/14077
from concurrent.futures import ThreadPoolExecutor
import numpy as np
import pytest

@pytest.fixture(scope="module")
def pool():
    yield ThreadPoolExecutor(max_workers=1)

def test_1(pool):
    # warm the thread
    pool.submit(lambda: None).result()

@pytest.mark.filterwarnings("ignore::RuntimeWarning")
def test_2(pool):
    # In the gil-enabled build (or with context_aware_warnings=0),
    # the filters established by the decorator also apply to the
    # lambda being executed by the pool thread.  With
    # context_aware_warnings=1, the warning is not filtered.
    pool.submit(lambda: np.array(0.0) / np.array(0.0)).result()


###################################################################

def test_3(pool):
    # This works as expected since catch_warnings() runs in the
    # worker thread.
    def work():
        with warnings.catch_warnings(category=RuntimeWarning, action='ignore'):
            return np.array(0.0) / np.array(0.0)
    pool.submit(work).result()