ImportError with from . import x on simple python files - python-3.x

Question

I wanted to port some code from python 2 to python 3 and it failed on an import error. So I tried to get rid of the porting itself and focus on the import by creating 2 basic python files to test with. However I can't even get those to work.
So I have 2 files
test.py:
print('Test works')
and test2.py:
from . import test
The result however is this error in Pycharm:
ImportError: cannot import name 'test' from '__main__'
(C:/Users/Username/test2.py)
In Ubuntu Shell:
Traceback (most recent call last): File "test2.py", line 1, in
from . import test1 SystemError: Parent module '' not loaded, cannot perform relative import
How can I solve it?

Answer 1

This "folder structure matters" is a large problem in python3. Your folder structure should NOT matter when coding, but should be referenced properly.
I've just resorted to using if/else depending on if ran locally or as part of a module:
if __name__ == "__main__": # Local Run
import test
else: # Module Run, When going production - delete if/else
from . import test

Answer 2

In Python3
test2.py:
import test
test.py:
if __name__ == "__main__":
print('Test works')
If you want to print "Test works" in other file
test2.py:
import test
test.main()
test.py:
def main():
print('Test works')
if __name__ == "__main__":
main()

Answer 3

The folder structure matters. You didn't name your module; I will call it foo. Put things in the right place:
$ mkdir foo
$ touch foo/__init__.py
$ mv /some/place/{test1,test2}.py foo/
Notice that python -c 'import test' works already, even before you wrote your test.py file. To avoid confusion I recommend naming your file test1.py.
The way you call your code matters. Verify that . dot is in sys.path:
$ export PYTHONPATH=.
$ python -m foo.test1
Alternatively this should work, if you prefer:
$ python foo/test1.py
EDIT:
I answered question #1, and OP now asks question #2, about this diagnostic:
ImportError: cannot import name 'test' from 'main' (C:/Users/Username/test2.py)
Please organize your files in the proper structure. You need to put test2.py within a foo/ directory (or whatever you care to call it). You need to create an empty foo/__init__.py file, as that is important for the import machinery.
Also, the PYTHONPATH env var in the calling environment matters. In addition to the command line environment, you have now introduced a PyCharm environment. Take care to configure PyCharm correctly for your project. Click on Preferences -> Project Structure and ensure that foo shows up as a Source Folder. You can debug this in either environment by executing these lines:
import sys
import pprint
pprint.pprint(sys.path)
Since import test would succeed even without your project being in place, I recommend you rename to test1.py and use import test1 so you can be sure you're pulling in your code.

Answer 4

I had the same problem, and ended up removing the "from . " that was added from the 2to3 conversion script.