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ViewsWhat is the correct folder structure to use for a Python project using pytest?
I try to organized my Python projects using a folder structure. When I need to make tests I use something like the following.
.
|-- src
| |-- b.py
| `-- main.py
`-- tests
`-- test_main.py
There is just one big problem with this approach. Pytest won't run if main.py is importing b.py.
So far I've tried placing empty __init__.py files inside the src and tests folders, both independently and together, but any of those seems to work.
It seems to me this is a pretty standard project, but I haven't been able to find a solution online. Should I use a different folder structure? Is there any recommended way to use pytest with this kind of projects?
This are the contents of the files:
# b.py
def triplicate(x):
return x * 3
# main.py
from b import triplicate
def duplicate(x):
return x * 2
# test_main.py
from src.main import duplicate
def test_duplicate():
assert duplicate(2) == 4
And this is the error I get when running pytest:
==================================================================================================== ERRORS ====================================================================================================
_____________________________________________________________________________________ ERROR collecting tests/test_main.py ______________________________________________________________________________________
ImportError while importing test module 'C:\Users\edwar\test_pytest\tests\test_main.py'.
Hint: make sure your test modules/packages have valid Python names.
Traceback:
c:\python39\lib\importlib\__init__.py:127: in import_module
return _bootstrap._gcd_import(name[level:], package, level)
tests\test_main.py:1: in <module>
from src.main import duplicate
src\main.py:1: in <module>
from b import triplicate
E ModuleNotFoundError: No module named 'b'
=========================================================================================== short test summary info ============================================================================================
ERROR tests/test_main.py
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Interrupted: 1 error during collection !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
=============================================================================================== 1 error in 0.15s ===============================================================================================
2 answers
Answer question0
You can put your source files in the root directory and adjust the import paths as such:
main.py
# main.py
from stackoverflow.b import triplicate
def duplicate(x):
return x * 2
b.py
# b.py
def triplicate(x):
return x * 3
test_main.py
# test_main.py
from stackoverflow.main import duplicate
def test_duplicate():
assert duplicate(2) == 4
Then running pytest . from the root directory stackoverflow:
collected 1 item
tests\test_main.py . [100%]
====================================================================================== 1 passed in 0.03s =======================================================================================
Or, if you wish to keep the src folder, your import would be this:
from stackoverflow.src.b import triplicate
0
Python uses the 'environment variable' PYTHONPATH to look for sources to import code from. By default, the directory you execute a python program is automatically included, but you want to include something like this when you test:
PYTHONPATH=$PYTHONPATH,../src python test_main.py
This is if you're executing a test from the source directory. Tools like IntelliJ (PyCharm) will let you add this as a value in your test invocation. Alternatively you can use export PYTHONPATH=.... (Note this is for a *nix environment, your mileage on windows may vary.)
The upshot is that every directory in PYTHONPATH will be loaded and Python will attempt to use it as a 'root' for modules you try to import. Your basic directory structure is the most idiomatic.
- See this answer for more on configuring
PYTHONPATHcorrectly. - See this doc for more about how the
PYTHONPATHis modified and used 'under the hood'. - See this answer for options to include the
srcdirectory when runningpytesttests. - See this blog post about using
autoenv(a Python library) to enable the usage of.envfiles to manage this for you (at least within avirtualenvsetup - a good idea generally). setup.pyis also idiomatic for including many modules, and may provide a more convenient path for the situation you're handling.