Reuse a fixture with parameters from another fixture

[Wovchena]

Downloading images from the Internet is flaky. I'm trying to reuse the images in tests to reduce instability. I also want the images to be removed from memory after they aren't needed. I'm trying to achieve that with the following code

import pytest @pytest.fixture(scope="module") def image(request): print(f"image-{request.param}") return f"image-{request.param}" @pytest.fixture(scope="module") def images(request): print(f"images{request.param}") values = [] for val in request.param: request._pyfuncitem.callspec.params["image"] = val request._pyfuncitem.callspec.indices["image"] = 0 request._pyfuncitem.callspec._arg2scope["image"] = request._pyfuncitem.callspec._arg2scope["images"] values.append(request.getfixturevalue('image')) return "images[" + ' '.join(values) + "]" @pytest.mark.parametrize("image", [1, 2], indirect=True) def test_image(image): print(f"test_image: {image}") @pytest.mark.parametrize("images", [[], [1], [1, 2, 3]], indirect=True) def test_images(images): print(f"test_images: {images}")

test_images[images2] prints test_images: images[image-1 image-1 image-1] instead of 1, 2, 3. I'd like request.getfixturevalue() to have a parameter to be passed to the fixture. I've checked pytest-lazy-fixture but its fixtures cannot be parametrized (https://stackoverflow.com/a/62166129/25242963).

[RonnyPfannschmidt]

Due to the removal of relevant context all i can say with the code provided is make the parameter a own fixture and stop missing with the internals

[Wovchena]

What context is missing?
Can you link an example to make the parameter a own fixture

[webknjaz]

from dataclasses import dataclass import pytest @dataclass class DataShape: param1: int param2: str @pytest.fixture def common_params(request: pytest.FixtureRequest) -> DataShape: return request.param @pytest.fixture def param1(common_params: DataShape) -> int: return common_params.param1 @pytest.fixture def param2(common_params: DataShape) -> str: return common_params.param2 @pytest.fixture def stash(param2: str) -> str: return param2 @pytest.mark.parametrize(  'common_params',  (DataShape(42, 'криївка'), ),  indirect=True, ) @pytest.mark.usefixtures('common_params') def test_accessing_param2(stash: str) -> None: assert stash == 'криївка'

[Wovchena]

Suppose param1 is complex data derived from 42. And param2 is complex data derived from криївка. I'm trying to avoid constructing param1 if a test requires just param2 and if test_accessing_param2() is the only requested test to run. At the same time there's another test that requires the whole DataShape. If both tests are requested, param2 should be created only once. I tried to illustrate this here:

import pytest def flaky_computation1(param1): return param1 + 1 def flaky_computation2(param2): return param2 + "!" class DataShape: def __init__(self, param1: int, param2: str): self.param1 = flaky_computation1(param1) self.param2 = flaky_computation2(param2) @pytest.fixture def common_params(request: pytest.FixtureRequest) -> DataShape: return request.param @pytest.fixture def param1(common_params: DataShape) -> int: return common_params.param1 @pytest.fixture def param2(common_params: DataShape) -> str: return common_params.param2 @pytest.fixture def stash(param2: str) -> str: return param2 @pytest.mark.parametrize(  'common_params',  (DataShape(42, 'криївка'), ), # shouldn't call flaky_computation1()  indirect=True, ) @pytest.mark.usefixtures('common_params') def test_accessing_param2(stash: str) -> None: assert stash == 'криївка!' @pytest.mark.parametrize(  'common_params',  (DataShape(42, 'криївка'), ), # should be reused from the parameter of test_accessing_param2  indirect=True, ) def test_full(common_params) -> None: assert str(common_params.param1) + common_params.param2 == "43криївка!"

[The-Compiler]

Converting this into a discussion because I don't see anything actionable for pytest here.