python django settings perform sql statement

Question

I want to define a constant variable in my settings.py file, that will be available in the entire app.
i.e. if I do in my settings.py, for example:
VAR = [1,2,3]

then in my view I can access it like:
var = settings.VAR

But, I want that VAR will be fetched from a database.
means, when my app starts, SQL is performed and loads the answer to VAR.

So I've attempted to create a function in views.py that does that:

in views.py:

def loadVAR():  
... # perform sql 
return VAR

and in settings.py:

import myapp.views  
VAR = myapp.views.loadVAR() 

But it does not work and I get an "500 Internal server error" I also haven't managed to perform the SQL directly in settings as well.

How can I achieve this ?

Answer 1

You can achieve this using middleware before touching the view,

class ModelMiddleware(object):
    """
        Model data
    """
    def process_request(self, request):

        # Fetch your data
        # Append var data to request
        request.META['VAR'] = [1, 2, 3]
        return None

You can get the VAR in view using request,

def veiw_data(request, ):
    print request.META['VAR']

Here is How to set django middleware in settings file

Update:

If you want to call the sql only first time project loads use this way,

I imagined my project structure this way,

mysite/
   mysite/
     __init__.py --> Add the logic in this file,
     urls.py
     settings.py
     test.py
   manage.py

__init__.py

from catalog.models import Product
import settings

settings.VAR = Product.objects.all()

Done. You can access the VAR in your project. Hope this may be helpful

Answer 2

settings.py is not meant to be used that way, if you want to store some settings in a database, consider using some external package which was designed for that, here is the list of some of them.