Why pytest always says " ImportError: attempted relative import with no known parent package"

Question

I'm new to pytest and python. My project structure is :

projroot/
|-src/
  |-a.py
|-test/
  |-test_a.py

and test_a.py is:

from ..src import a
def test_a():
  pass

Then run pytestunder projroot:

projroot>pytest

And always there is the error info: E ImportError: attempted relative import with no known parent package. Python verison: 3.8 on windows 10 x64. I read a lot articles and blogs and official suggestions, but still failed to figure out. Help me, please!

Answer 1

I found I must add __init__.py in test and projroot. __init__.py in src is not necessary. And pytest could run correctly in 3 folders:

# parent folder of project root
C:\>pytest projroot

# project root
C:\>cd projroot
C:\projroot>pytest

# test folder
C:\projroot>cd test
C:\projroot\test>pytest

Answer 2

By including a setup.py file in root directory and init.py in every folder worked for me and for importing a package inside any file just give that package location from parent directory

setup.py

from setuptools import setup, find_packages

setup(name="PACKAGENAME", packages=find_packages())

projroot/
|-__init__.py
|-setup.py
|-src/
  |-a.py
  |-__init__.py
|-test/
  |-test_a.py
  |-__init__.py

from src import a
def test_a():
  pass

Reference https://docs.pytest.org/en/6.2.x/goodpractices.html