pytest: parameterize fixtures in a DRY way

You could try to pass the settings as a dictionary parameter to the fixture, something like this:

import pytestfrom myapp import create_app@pytest.fixturedef app(request):    settings_override = {        'SQLALCHEMY_DATABASE_URI': "sqlite:///:memory:",    }    params = request.param if hasattr(request, 'param') else {}    return create_app({**settings_override, **params})@pytest.fixturedef db(app):    do_something_to_create_the_database(app)    yield dbdef test_my_application_no_override_params(db, app):    ...@pytest.mark.parametrize("app", [{'BAZ': True}], indirect=True)def test_my_application_1(db, app):    ...@pytest.mark.parametrize("app", [{'FOO': 'BAR'}], indirect=True)def test_my_application_2(db, app):    ...

The request object gives the fixture access to the requesting test context and can be used as an argument in any fixture.
The indirect=True argument in the pytest.mark.parametrize decorator passes the parameter to the optional param attribute of the request object, so this essentially parametrizes the fixture itself.

UPDATE:
I added the helpful addition (usage of hasattr) as proposed by @JoeJ, which makes it possible to use a test without the additional parameters.