Why pytest collect and run my cases twice when Im not using the if __name__ == '__main__' expression

[TapH3ro]

sorry for my poor English...

python version: 3.10.11
I created a new project, and created 2 .py files: test_demo.py and start_test.py; and only installed pytest 8.0.2 in my python interpreter.

test_demo.py

class TestDemo:

    def test_001(self):
        assert 1 == 1

start_test.py

import pytest \n
arg = ['-s', '-v', '-k', 'test_demo.py']
pytest.main(arg)

when i run the start_test.py, it gives me this:

============================= test session starts =============================
platform win32 -- Python 3.10.11, pytest-8.0.2, pluggy-1.4.0 -- C:\Users\amber\AppData\Local\Programs\Python\Python310\python.exe
cachedir: .pytest_cache
metadata: {'Python': '3.10.11', 'Platform': 'Windows-10-10.0.22631-SP0', 'Packages': {'pytest': '8.0.2', 'pluggy': '1.4.0'}, 'Plugins': {'allure-pytest': '2.13.5', 'anyio': '4.4.0', 'flaky': '3.8.1', 'html': '4.1.1', 'metadata': '3.1.1', 'ordering': '0.6', 'xonsh': '0.18.3'}, 'JAVA_HOME': 'D:\\Jdk'}
rootdir: C:\Users\amber\Desktop\ArdAuto
configfile: pytest.ini
plugins: allure-pytest-2.13.5, anyio-4.4.0, flaky-3.8.1, html-4.1.1, metadata-3.1.1, ordering-0.6, xonsh-0.18.3
collecting ... ============================= test session starts =============================
platform win32 -- Python 3.10.11, pytest-8.0.2, pluggy-1.4.0 -- C:\Users\amber\AppData\Local\Programs\Python\Python310\python.exe
cachedir: .pytest_cache
metadata: {'Python': '3.10.11', 'Platform': 'Windows-10-10.0.22631-SP0', 'Packages': {'pytest': '8.0.2', 'pluggy': '1.4.0'}, 'Plugins': {'allure-pytest': '2.13.5', 'anyio': '4.4.0', 'flaky': '3.8.1', 'html': '4.1.1', 'metadata': '3.1.1', 'ordering': '0.6', 'xonsh': '0.18.3'}, 'JAVA_HOME': 'D:\\Jdk'}
rootdir: C:\Users\amber\Desktop\ArdAuto
configfile: pytest.ini
plugins: allure-pytest-2.13.5, anyio-4.4.0, flaky-3.8.1, html-4.1.1, metadata-3.1.1, ordering-0.6, xonsh-0.18.3
collecting ... collected 1 item

test_demo.py::TestDemo::test_001 PASSED

============================== 1 passed in 0.05s ==============================
collected 1 item

test_demo.py::TestDemo::test_001 PASSED

============================== 1 passed in 0.24s ==============================

Process finished with exit code 0

however when i added the if name == 'main' expression

============================= test session starts =============================
platform win32 -- Python 3.10.11, pytest-8.0.2, pluggy-1.4.0 -- C:\Users\amber\AppData\Local\Programs\Python\Python310\python.exe
cachedir: .pytest_cache
metadata: {'Python': '3.10.11', 'Platform': 'Windows-10-10.0.22631-SP0', 'Packages': {'pytest': '8.0.2', 'pluggy': '1.4.0'}, 'Plugins': {'allure-pytest': '2.13.5', 'anyio': '4.4.0', 'flaky': '3.8.1', 'html': '4.1.1', 'metadata': '3.1.1', 'ordering': '0.6', 'xonsh': '0.18.3'}, 'JAVA_HOME': 'D:\\Jdk'}
rootdir: C:\Users\amber\Desktop\ArdAuto
configfile: pytest.ini
plugins: allure-pytest-2.13.5, anyio-4.4.0, flaky-3.8.1, html-4.1.1, metadata-3.1.1, ordering-0.6, xonsh-0.18.3
collecting ... collected 1 item

test_demo.py::TestDemo::test_001 PASSED

============================== 1 passed in 0.04s ==============================

Process finished with exit code 0

[RonnyPfannschmidt]

The start script has a filename that is searched for tests

Searching tests is done after import

It's strongly recommended to keep all scripts importable without triggering a execution

[TapH3ro]

i love you...
This is my first discussion on github, and you make me feel this is a brilliant site

[RonnyPfannschmidt]

It's a pleasure to help

Everyone was a beginner at some point and it's a joy to see people grow and evolve as they take in and progress