Django check at runtime if code is executed under "runserver command" or not

Question

I've got a project based on django, that wraps some custom code.

During import, this code is loading some heavy file to be executed. I need to check whether imports are executed under "runserver command" or not. This way I can prevent loading heavy files during django installation.

How can I check if code is executed under runserver command?

• willeM_ Van Onsem: Why not just set an environment variable and check that way? So MY_VAR=1 python manage.py runserver, then you can use sys.environ('MY_VAR) == '1'?
• David Maze: You'd probably be better off fixing the actual issue: you shouldn't do significant work when a file is imported, move the actual loading and computation inside some sort of function that you can call as needed. This will also be a problem for you in scenarios like unit testing, where you need the code available and may or may not want the expensive object load.
• Domenico Monaco: David, yes I agree, but in the project we use external library that by default has initialization with heavy files.
• Vegard: This question is similar to: How can I tell whether my Django application is running on development server or not?. If you believe it’s different, please edit the question, make it clear how it’s different and/or how the answers on that question are not helpful for your problem.

Answer 1

You can probably hack this into the handle of the runserver command, through monkey patching, i.e.:

# bad idea!!
GLOBAL_VAR = {
 'AS_RUNSERVER': False,
}
from django.core.management.commands.runserver import Command
old_handle = Command.handle
def new_handle(self, *args, **kwargs):
 GLOBAL_VAR['AS_RUNSERVER'] = True
 old_hande(self, *args, **kwargs)
Command.handle = new_handle

but I would advise to make this more clean, and work with an environment variable, like:

import sys
if os.environ.get('ENV_AS_RUN_SERVER') == '1':
 # ...

and then run this with:

ENV_AS_RUN_SERVER=1 python manage.py runserver

Answer 2

You can override the runserver command to do whatever you want, it's a normal management command.

# your_app/management/commands/runserver.py
from django.conf import settings
from django.contrib.staticfiles.management.commands.runserver import Command as RunserverCommand
class Command(RunserverCommand):
 def add_arguments(self, parser):
 super().handle(self, parser)
 # you can add additional arguments here, maybe to decide whether you
 # should load your file or not
 def handle(self, *args, **kwargs):
 . . .
 # do special things here
 . . .
 super().handle(*args, **kwargs)

But you need to make sure the app housing this management command is installed before django.contrib.staticfiles in your INSTALLED_APPS setting.

INSTALLED_APPS = [
 . . .
 'your_app',
 . . .
 # load this after your_app so custom runserver command loads first
 'django.contrib.staticfiles',
]