Python3: Attempted relative import in non-package

Question

I'm so sorry about this basic question, because it's similar to this: Stumped by relative imports

But I'm trying to follow the PEP328 http://www.python.org/dev/peps/pep-0328/#guido-s-decision and it doesn't work for me :(

These are my files:

dev@desktop:~/Desktop/test$ ls
controller.py  __init__.py  test.py

2to3 says all it's right:

dev@desktop:~/Desktop/test$ 2to3 .
RefactoringTool: Skipping implicit fixer: buffer
RefactoringTool: Skipping implicit fixer: idioms
RefactoringTool: Skipping implicit fixer: set_literal
RefactoringTool: Skipping implicit fixer: ws_comma
RefactoringTool: No files need to be modified.

The content of the files:

dev@desktop:~/Desktop/test$ cat controller.py 
class Controller:
    def __init__(self):
        pass

dev@desktop:~/Desktop/test$ cat __init__.py 
# -*- coding: utf-8 -*-

dev@desktop:~/Desktop/test$ cat test.py 
#!/usr/bin/env python
from .controller import Controller 
if __name__ == '__main__':
    print('running...')

But the import it's not working:

dev@desktop:~/Desktop/test$ python3 test.py 
Traceback (most recent call last):
  File "test.py", line 2, in <module>
    from .controller import Controller 
ValueError: Attempted relative import in non-package
dev@desktop:~/Desktop/test$ 

Any help is appreciated! Thanks in advance!

Answer 1

You cannot use a script within a package; you are running test, not test.test. A top-level script can thus not use relative imports.

If you wanted to run a package as a script, you'd need to move test/test.py to testpackage/__main__.py, move one directory up in your shell to ~/Desktop and tell python to run a package with python -m testpackage.

Demo:

$ ls testpackage/
__init__.py   __main__.py   __pycache__   controller.py
$ cat testpackage/controller.py 
class Controller:
    def __init__(self):
        pass

$ cat testpackage/__init__.py 
# -*- coding: utf-8 -*-

$ cat testpackage/__main__.py 
from .controller import Controller
if __name__ == '__main__':
    print('running...')

$ python3.3 -m testpackage
running...

You cannot name the package test; Python already has such a package for the test suite and that'll be found before a package in the current working dir is found.

The alternative is to create a script outside of the package and import the package from the script.