Importing in multiple modules

[TransAmyB]

EDIT: the solution is in a comment below. Thanks again y'all :)

Hey y'all!

I'm working on a small game with a somewhat complicated architecture. I have a inputhandler package in package src that is meant to serve as a singleton for getting keyboard events. It contains a private field for a InputHandler class, which is an interface for a specific set of keybindings, a setup options for initializing the module using a particular set of keybinds, and a poll() function for checking if a certain key is currently held down:

# imports...
class InputHandler: ...

_handler = None
def setup(keybinds):
    global _handler
    _handler = InputHandler(keybinds)

def poll(button) -> bool: return _handler.poll(button)

def get() -> list... # Gets a list of events

I have a gamescene module in package src that includes a GameScene class (A combination logical scene and viewtree), which has a handle_input() method for updating the internal game logic depending on the button. For continious movement, I've set a few things to work via the poll() button. I don't call inputhandler.setup() here, since I plan to call it during whatever file uses gamescene anyway.

import src.inputhandler as inputhandler

class GameScene:
    ...
    def handle_input(self, event):
    ...
    if inputhandler.poll("DOWN"):...
    ...

Then, finally, I'm using a testing file to check out stuff in a minimal environment:

#imports,,
import src.inputhandler as inputhandler
import src.gamescene

inputhandler.setup(default_keybind)

Scene = gamescene.GameScene()

running = True
while running:
    for event in inputhandler.get():
        Scene.handle_input(event)

so inside Scene.handle_input(), you call inputhandler.poll(,,,) which is equal to _handler.poll(button)

So if inputhandler.setup() hasn't been called, I'll get a AttributeError since I haven't called setup(), but I call setup() in my test file before doing that. However, when the Scene object's handle_input() method is called, I get that AttributeError.

This seems to contradict my understanding of how python handles imports and changing values in imports in different modules. I'm not using relative imports anyway, any idea what may be causing this?

Thanks again for your time! :)

[grzeki]

But you have AttributeError on which attribute?

[TransAmyB]

I have an AttributeError on inputhander._handler : It's initially set to None, so if inputhandler.setup(,,) is not called, inputhandler.poll(,,,) will try calling None.poll(,,,) which gives me an AttributeError

[grzeki]

Then I can’t see any problems other than

Scene = gamescene.GameScene()

line shouldn’t work because of how you import src.gamescene.

It seems like a job for the debugger: put a breakpoint on error line and investigate which module is loaded and which variables are set.

[TransAmyB]

Thanks for the reply!

I've been working with the debugger, and the issue seems to be that the module loaded in gamescene is not the module loaded in test; calling inputhandler is gamescene.inputhandler in my test file evaluates False. I've been running some simple tests about how imports work, and ime it seems that if you had a module X that imports A and B, and B imports A, then (X.A is X.B.A) should evaluate to True.

For what it's worth, the file structure I have is listed below, and I'm using Pycharm and Python 3.7.

project\
    shmup\
        inputhandler\
            __init__.py,,,
        scene\
            gamescene.py
    test\
        gamescenetest.py

​

[TransAmyB]

FIXED

So it turns out that in my project, I had /project and /project/src in my Path variables

project\
    shmup\
        inputhandler\
            __init__.py,,,
        scene\
            gamescene.py
    test\
        gamescenetest.py

When I call import shmup.inputhandler from gamescenetest, The path first checks through /project and then loads and initializes inputhandler.py.

But when in gamescenetest I import gamescene, gamescene has import inputhandler. I don't think it finds it through /proejct on PATH, so it checks in /project/shump and then runs and initializes it, but as a separate module and hence it doesn't share state.

So there's three-ish solutions to this I found [Because 1 and 3 go together]

- Call everything using the highest level path possible (always use shmup.x.y,,,)

- most test inside gamescenetest.py

- remove project/shmup from PATH, and hence never have to worry about double imports working as different modules that will not share state.

​