Problems with relative imports and pep 366

[Gabriele Lanaro]

I've yet asked this question on SO, I'll copy the contents:

I have a "canonical file structure" like that (I'm giving sensible names
to ease the reading):

mainpack/

  __main__.py
  __init__.py 

  - helpers/
     __init__.py
     path.py

  - network/
     __init__.py
     clientlib.py
     server.py

  - gui/
     __init__.py
     mainwindow.py
     controllers.py

In this structure, for example modules contained in each package may
want to access the helpers utilities through relative imports in
something like:

# network/clientlib.py
from ..helpers.path import create_dir

The program is runned "as a script" using the __main__.py file in this
way:

python mainpack/

Trying to follow the PEP 366 I've put in __main__.py these lines:

___package___ = "mainpack"
from .network.clientlib import helloclient 

But when running:

$ python mainpack 
Traceback (most recent call last):
  File "/usr/lib/python2.6/runpy.py", line 122, in _run_module_as_main
    "__main__", fname, loader, pkg_name)
  File "/usr/lib/python2.6/runpy.py", line 34, in _run_code
    exec code in run_globals
  File "path/mainpack/__main__.py", line 2, in <module>
    from .network.clientlib import helloclient
SystemError: Parent module 'mainpack' not loaded, cannot perform relative import

What's wrong? What is the correct way to handle and effectively use
relative imports?

I've tried also to add the current directory to the PYTHONPATH, nothing
changes.

link:
http://stackoverflow.com/questions/2943847/nightmare-with-relative-imports-how-does-pep-366-work