Question

I shall simplify the code slightly in the hopes that someone can shed some light on this and maybe give me a more pythonic approach if what im doing is wrong.

Inside dbcontrollers.py

import autosettings
import aerialcontroller
import controller
import gobject
import gtk
import utils

# Create the settings object so we can call and edit settings easily
SETTINGS = autosettings.autoSettings()
CONTROLLERS = {}

class dBControllers(object):

    def __init__(self):

        # This works happily so nothing wrong in autosettings module
        print SETTING.last_port
        port_to_use = SETTINGS.last_port

if __name__ == "__main__":

    # Create an object that holds all the GTK stuff (when not simplified)
    dBControllers = dBControllers()
    aerialController = aerialcontroller.aerialController()

Inside aerialcontroller.py

class aerialController(object):

    def __init__(self):

        self.motor_number = str(SETTINGS.aerial_motor_number)
        CONTROLLERS[self.motor_number] = self

But when I run this, I get “NameError: global name ‘SETTINGS’ is not defined”.

I don’t really understand how this is supposed to work, sharing global variables accross modules. I assume this is not the correct way to do things like this, so can someone point me in the right direction.

Thank-you.

P.S. Simply code examples would be beneficial – still a relative newcomer to python.

Answer 1

Python doesn’t have a way to share a name across modules. If there’s something you want access to from multiple modules, you declare it in a separate module (e.g. “settings”), and then import it wherever you want it.

settings.py:

SETTINGS = autosettings.autoSettings()
CONTROLLERS = {}

aerialcontroller.py

from settings import SETTINGS, CONTROLLERS
class aerialController(object):

    def __init__(self):
        self.motor_number = str(SETTINGS.aerial_motor_number)
        CONTROLLERS[self.motor_number] = self

N.B. Doing from settings import SETTINGS will work as long as you only want to modify SETTINGS. If you want to completely replace it with a new set of settings (SETTINGS = ...) you need to do import settings, and refer to it as settings.SETTINGS.

This is by design: if modules got variables from the script that imported them, it would be much harder to see where they came from when reading the code (and importing the module from somewhere else might not work). Doing it this way, you can always see where the variable came from within each file (well, almost always: please don’t overuse from <name> import *).