Where shall I put 'initialization code' in a Django application?

I want some code in my Django app to be executed only once when server is started, not per request.

Specifically, I want to load some database tables into memory. These tables contain some 'metadata' that doesn't change per request. Like this:

ProductTypesData = None;def loadProductTypesData():     productTypes = ProductType.objects.all();     for ptype in productTypes:         ptype_data = {"id":ptype.id,"name": ptype.name,"description":ptype.desc         };         ProductTypesData.append(ptype_data);loadProductTypesData();

Where should I put this code?Other Q/A about django initialization suggest to put it in urls.py. But importing the models in urls.py doesn't seem logical to me.

Can I just put the code in models.py? Does it get executed only once (if it is acceptable to be executed not on django start)?