# settings.settings.py

INSTALLED_APPS = localsettings.INSTALLED_APPS + (
    ...
    'apps.myapp',
)

MIDDLEWARE_CLASSES = (
    'apps.myapp.initialize.MyAppConfig',
    ...
)


# apps.myapp.models.py

from django.db import models


class Game(models.Model):
    name = models.CharField(max_length=30)
    plays = models.PositiveIntegerField()


# apps.myapp.initialize.py

from django.core.exceptions import MiddlewareNotUsed

from .models import Game


class MyAppConfig(object):
    name = 'apps.myapp'
    run_already = False

    def __init__(self):
        if not self.run_already:
            try:
                # If you want to call Save() and emit all its signals:
                for game in Game.objects.all():
                    game.plays = 0
                    game.save()

                # Or, if you want to update without calling any signals:
                Game.objects.update(plays=0)

            except Exception, err:
                    print err
                    pass

            self.run_already = True
        raise MiddlewareNotUsed('Startup complete')