How to set up Python packages

Question

I want this structure:

Zimp/controller/game_play -->How do I: import Zimp/model/game_play module in the easiest way? Zimp/model/game_play

I made a folder called controller and a folder called model. Within those folders I put an empty __init__.py file (don't know why that would do anything). I didn't make a model.py file or a controller.py file. It didn't work. I just made a model.py and a controller.py that are empty except for the main block that automatically appears when creating a new module. No difference.

In controller/game_play.py I tried: from ..model import game_play_model

It says value error: attempted relative import in non-package

Is the idea not to actually put them in separate directories? What is the norm?

Thanks

Answer 1

The problem is you're trying to execute a subpackage module directly, see answers to the question Attempted relative import in non-package even with __init__.py.

First I think you need to set up your directory file structure like this:

Zimp/ top-level package
 __init__.py package initalization
 controller/ subpackage
 __init__.py subpackage initalization
 game_play.py subpackage module
 model/ subpackage
 __init__.py subpackage initalization
 game_play_model.py subpackage module

The __init__.py files can all be empty as they just indicate that the directory is a [sub]package.
For illustrative purposes let's say thegame_play_model.pyfile contained:

print 'hello from game_play_model.py'

and thegame_play.pyfile contains the following to detect when it was being executed directly and adds the name of the parent of its folder — Zimp — to the Python search path — thus allowing you to then directly import other things from the package when it's run that way.

if __name__ == '__main__' and __package__ is None:
 import sys, os.path as path
 # append parent of the directory the current file is in
 sys.path.append(path.dirname(path.dirname(__file__)))
import model.game_play_model
print 'hello from game_play.py'

And you executed it directly with something likepython game_play.pyit would output:

hello from game_play_model.py
hello from game_play.py

• user3164083: Thanks I have that file structure and code but it still won't recognise a module named model.game_play_model. My zimp folder also has a pycache_ folder in it if that makes a difference. I copeied your if statement word for word. Not sure I was meant to.
• martineau: The if statement and sys.path.append() call have to appear before the import statement.
• martineau: Note you can also use sys.path.append(path.abspath(path.join(path.dirname(__file__), '..'))) which some feel is clearer about what's being done.
• martineau: This would be even better IMHO: sys.path.append(path.dirname(path.dirname(__file__))).

Answer 2

from Zimp.model import game_play

Should do the trick.

• user3164083: Thanks. I got "no module named Zimp.model". I only made Zimp as a folder..So I should create a new module named zimp. And inside it what should I write? Thank you!!
• Ruben: I think it might be better if you read up on how Python modules work: docs.python.org/2/tutorial/modules.html
• user3164083: Thanks, I have already read that. It doesn't say how to create the structure. Only how to work with it once it is done.
• Ruben: Are you sure? ;) docs.python.org/2/tutorial/modules.html#packages. In short, packages are just (sub) directories. Just make sure you have a __init__.py file inside the directory. Otherwise it's not recognised as a package/module. Hope that helped.
• user3164083: Thanks, but I do have that file in the directories :(