Correct place to put extra startup code in django?

I would like to run some environment checks when my django process starts and die noisily in t开发者_运维百科he case of an error. I'm thinking things like the database has an incorrect encoding or the machine has a python version we don't support.

I'd rather our team be faced with a fatal error that they have to fix, rather than be able to ignore it.

I'm Ok with writing these checks but I'm curious about where the best place to put them is. How do I get them to execute as part of django's startup process? I thought there might be a signal I could listen too, but I can't find a relevant one in the docs.

If you don't want to use settings module, then try project's __init__.py.

If you want to check that the system is correctly installed, I think that you should write your own admin command and run it as post-installation check.

I think that it doesn't worth to check if the python version is correctly installed too often especially if you are installing the django app on shared-host. My app is hosted at alwaysdata and they restart the FastCgi process every hour. These checks can have an impact on the application response time.

We use the top-level urls.py for this.

I would put them in settings.py. In the past, I have put system checks like this:

try:
    from local_settings import *
except ImportError:
    print "Missing %s" % os.path.join(PROJECT_ROOT, "local_settings.py")

if DEBUG:
    for p in [PROJECT_ROOT, MEDIA_ROOT, THEME_DIR, ADMIN_MEDIA_ROOT] + list(TEMPLATE_DIRS):
        p = os.path.normpath(p)
        if not os.path.exists(p):
            print "Missing path: %s" % p

I have tested all three __init__.py Settings.py and urls.py methods and this is what I have found.

When code is run from either __init__.py or Settings.py, the start up functions are run twice upon web server start up; when the start up functions are run from urls.py the code is run once, however it is run only upon the first request made to the we server leading to a potentially long wait for the first user to visit your site.

It is standard practise to call a 'warming' page when bringing large web applications back online so I don't see that calling a start up function from a CLEARLY identified location in the urls.py should be a problem.

Most of the answers here are extremely old, so I assume that's why Django's checks framework isn't mentioned.

It's been a part of django since at least v2 (django==3.1 at the time of writing).

That's probably the right place for most of the checks you're requiring.

I'd still consider using settings, as mentioned by other answers, for checks where settings contents are required but which also need to be run prior to readying the apps.

You can put it in settings.py as mentioned by others, but having code in the settings is not ideal. There is also the option of adding a handler for django.db.models.signals.class_prepared that does the desired start up checks after a specific model class is prepared.