Doctest and relative imports

Question

I'm having trouble using doctest with relative imports. The simple solution is just to get rid of the relative imports. Are there any others?

Say I have a package called example containing 2 files:

example/__init__.py

"""
This package is entirely useless.
>>> arnold = Aardvark()
>>> arnold.talk()
I am an aardvark.
"""

from .A import Aardvark

if __name__ == "__main__":
    import doctest
    doctest.testmod()

example/A.py

class Aardvark(object):
    def talk(self):
        print("I am an aardvark.")

If I now attempt

python example/__init__.py

then I get the error

Traceback (most recent call last):
  File "example/__init__.py", line 8, in <module>
    from .A import Aardvark
ValueError: Attempted relative import in non-package

Rodneyrodolfo

I would get rid of the relative imports, many Python style guides strongly discourage them, most forbid them. – Lunch

@JasonScheirer Are there any examples for this discouragement? In projects like numpy these are very common. – Euratom

Answer 1

Create another file my_doctest_runner.py:

if __name__ == "__main__":
    import doctest
    import example
    doctest.testmod(example)

Execute my_doctest_runner.py to run doctests in example/__init__.py:

$ python2.7 my_doctest_runner.py
**********************************************************************
File "/tmp/example/__init__.py", line 4, in example
Failed example:
    arnold.talk()
Expected:
    I am an aaardvark.
Got:
    I am an aardvark.
**********************************************************************
1 items had failures:
   1 of   2 in example
***Test Failed*** 1 failures.

Pietje

Thanks for the answer. In the end I've ended up changing the relative import to an absolute one, (from example.A import Aadvark) based on Jason Scheirer's comment. – Rodneyrodolfo

Answer 2

Pytest's --doctest-modules flag takes care of relative imports:

$ ls example/
A.py  __init__.py
$ pytest --doctest-modules example
==================== test session starts ====================
...

example/__init__.py .                                 [100%]

===================== 1 passed in 0.03s =====================

Espy

Just note that this won't work well with relative imports in namespace packages, so you might need to place an empty __init__.py if you currently have none. – Trishatriskelion

Answer 3

Just do

from A import Aardvark

Ology

well, I am afraid this breaks python 3 compatibility. – Ashes

While this code may answer the question, it is better to explain how to solve the problem and provide the code as an example or reference. Code-only answers can be confusing and lack context. – Hardaway

Answer 4

As of pytest 6.0.0, importlib is a valid import mode. Using that solved the problem for me.

pytest --import-mode=importlib

Fortis