Using global variables between files?
The problem is you defined myList
from main.py
, but subfile.py
needs to use it. Here is a clean way to solve this problem: move all globals to a file, I call this file settings.py
. This file is responsible for defining globals and initializing them:
# settings.py
def init():
global myList
myList = []
Next, your subfile
can import globals:
# subfile.py
import settings
def stuff():
settings.myList.append('hey')
Note that subfile
does not call init()
— that task belongs to main.py
:
# main.py
import settings
import subfile
settings.init() # Call only once
subfile.stuff() # Do stuff with global var
print settings.myList[0] # Check the result
This way, you achieve your objective while avoid initializing global variables more than once.
See Python's document on sharing global variables across modules:
The canonical way to share information across modules within a single program is to create a special module (often called config or cfg).
config.py:
x = 0 # Default value of the 'x' configuration setting
Import the config module in all modules of your application; the module then becomes available as a global name.
main.py:
import config print (config.x)
In general, don’t use from modulename import *. Doing so clutters the importer’s namespace, and makes it much harder for linters to detect undefined names.