Difference between `scope` in `fixture` and `scope` in `parametrize` when using indirect parametrization

Question

I want to use indirect parametrization as shown in this answer and in pytest documentation.

I want to be able to set scope to be able to configure if fixture is run for every function or once for many of them.

However I see that I can set scope on fixture decorator:

import pytest

@pytest.fixture(scope="function")
def fixt(request):
    return request.param * 3

@pytest.mark.parametrize("fixt", ["a", "b"], indirect=True)
def test_indirect(fixt):
    assert len(fixt) == 3

Or on parametrize decorator:

import pytest

@pytest.fixture
def fixt(request):
    return request.param * 3

@pytest.mark.parametrize("fixt", ["a", "b"], indirect=True, scope="function")
def test_indirect(fixt):
    assert len(fixt) == 3

Or even both at the same time:

import pytest

@pytest.fixture(scope="function")
def fixt(request):
    return request.param * 3

@pytest.mark.parametrize("fixt", ["a", "b"], indirect=True, scope="function")
def test_indirect(fixt):
    assert len(fixt) == 3

What is the difference and when I should set each?

---

Update:

I tested each to see how they differ.

Code I used for testing:

import pytest

scope_fixture="function"
scope_parametrize="module"

with open('scope_log.txt', 'a') as file:
    file.write(f'--------\n')
    file.write(f'{scope_fixture=}\n')
    file.write(f'{scope_parametrize=}\n')

@pytest.fixture(scope=scope_fixture)
def fixt(request):
    with open('scope_log.txt', 'a') as file:
        file.write(f'fixture ' + str(request.param)+'\n')
    return request.param * 3

@pytest.mark.parametrize("fixt", ["a", "b"], indirect=True, scope=scope_parametrize)
def test_indirect1(fixt):
    with open('scope_log.txt', 'a') as file:
        file.write(f'1 ' + str(fixt)+'\n')
    assert len(fixt) == 3

@pytest.mark.parametrize("fixt", ["a", "b"], indirect=True, scope=scope_parametrize)
def test_indirect2(fixt):
    with open('scope_log.txt', 'a') as file:
        file.write(f'2 ' + str(fixt)+'\n')
    assert len(fixt) == 3

Results:

scope_fixture=None
scope_parametrize=None
fixture a
1 aaa
fixture b
1 bbb
fixture a
2 aaa
fixture b
2 bbb
--------
scope_fixture='function'
scope_parametrize=None
fixture a
1 aaa
fixture b
1 bbb
fixture a
2 aaa
fixture b
2 bbb
--------
scope_fixture='module'
scope_parametrize=None
fixture a
1 aaa
2 aaa
fixture b
1 bbb
2 bbb
--------
scope_fixture=None
scope_parametrize='function'
fixture a
1 aaa
fixture b
1 bbb
fixture a
2 aaa
fixture b
2 bbb
--------
scope_fixture=None
scope_parametrize='module'
fixture a
1 aaa
2 aaa
fixture b
1 bbb
2 bbb
--------
scope_fixture='function'
scope_parametrize='module'
fixture a
1 aaa
2 aaa
fixture b
1 bbb
2 bbb
--------
scope_fixture='module'
scope_parametrize='module'
fixture a
1 aaa
2 aaa
fixture b
1 bbb
2 bbb
--------
scope_fixture='module'
scope_parametrize='function'
fixture a
1 aaa
fixture b
1 bbb
fixture a
2 aaa
fixture b
2 bbb
--------
scope_fixture='function'
scope_parametrize='function'
fixture a
1 aaa
fixture b
1 bbb
fixture a
2 aaa
fixture b
2 bbb

Answer 1

As @Tzane pointed out in comment, setting the scope for parametrize overrides any scope set in fixtures.

From documentation:

scope (Optional[_ScopeName]) – If specified it denotes the scope of the parameters. The scope is used for grouping tests by parameter instances. It will also override any fixture-function defined scope, allowing to set a dynamic scope using test context or configuration.