run unit tests and coverage in certain python structure

Question

I have some funny noob problem.

I try to run unit tests from commandline:

H:\PRO\pyEstimator>python src\test\python\test_power_estimator.py
Traceback (most recent call last):
  File "src\test\python\test_power_estimator.py", line 2, in <module>
    import src.main.python.power_estimator as power
ImportError: No module named src.main.python.power_estimator

this same happens when I try to run it in desired folder:

H:\PRO\pyEstimator\src\test\python>python test_power_estimator.py

My folder structure looks like this.

├───src
│   │   __init__.py
│   │   __init__.pyc
│   │
│   ├───main
│   │   │   __init__.py
│   │   │   __init__.pyc
│   │   │
│   │   └───python
│   │       │   __init__.py
│   │       │   power_estimator.py
│   │       │   __init__.pyc
│   │       │   power_estimator.pyc
│   │       │
│   │       └───GUI
│   │               __init__.py
│   │
│   └───test
│       │   __init__.py
│       │
│       └───python
│               test_power_estimator.py
│               __init__.py
│               covrunner.bat
│               .coverage
│
└───doc

Maybe i don't see something obvious. I also try to run coverage. Is this approach good (file structure) ?

ddaa · Accepted Answer · 2009-11-14 11:54:57Z

1

The immediate issue you are facing is a misunderstanding of what is "local code" in Python (I am not sure if there is an official terminology, so I am making this one up) and how to import it.

When you run python src\test\python\test_power_estimator.py, the first element in sys.path is set to the directory containing the test_power_estimator.py script, not the current directory. So the statement "import src.main.python.power_estimator as power" looks for the package src in the directory src/test/python, and that fails.

One way to work around the issue is to set the PYTHONPATH environment variable to "H:\PRO\pyEstimator"

But the recommended way to run tests is to use a test runner script. I recommended using nosetest.

In addition, nosetest has support for collecting coverage data while running your tests.

Besides, it sounds like a bad idea to have a python package named "src". You should rename your package to be your project. Maybe "estimator" or "pyestimator" (lowercase, please).

answered Nov 14, 2009 at 11:54

ddaa

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4 Comments

bua Over a year ago

Hi, thanks for reply, what i've done to launch this project is : import sys import os sys.path.append(os.getcwd()) from src.main.python.power_estimator import * But i don't like that. I'll try PYTHONPATH instead. "SRC" Is it really that bad, while my root package directory names "estimator" and inside I've all project files, docs, SConstructs etc..?

ddaa Over a year ago

As long as there is a init.py file directly in the PyEstimator directory, that's mostly fine. The issue is that "src" is a name I would not put at the root of my module namespace. And either "src.main.python.power_estimator" is a relative import (fragile, bad!) or "src" is the package root name (kind of unhygienic).

bua Over a year ago

Thanks again. I'll certainly follow your remarks. Do You know any good resource in the network for some pragmatic approach in this area? I was basing on this: docs.python.org/tutorial/modules.html#packages and as we see this is not exhausting the good practices.

ddaa Over a year ago

PEP8 is a good baseline, but then a lot of details are a matter of judgement and experience.

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