Programmatically check if syncdb is running

I have some signal handlers that work on the Django user. Additionally I'm using South. These signal handlers depends on some migrations th开发者_如何学Pythonat must run in before.

When Django executed snycdb and creates the admin user these migrations haven't run and the signal handlers raise an exception.

I'm searching for a way to detect if Django currently runs syncdb so that the signal handerls can skip execution.

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I trap the DatabaseError exception and check if the ContentType entry for the model I'm trying to use exists, if it doesn't I assume syncdb is happening, otherwise rollback the transaction and re-raise the original exception. This method incurs in an extra DB access only when DatabaseError is raised.

    with transaction.commit_on_success():
        try:
            content_type = ContentType.objects.get_for_model(kwargs['instance'])
            for relation in WorkflowTypeRelation.objects.filter(content_type=content_type):
                workflow_instance = WorkflowInstance.objects.create(content_object=kwargs['instance'],
                    workflow_type=relation.workflow_type)
        except DatabaseError as database_error:
            try:
                ContentType.objects.get(model='workflowtyperelation')
            except ContentType.DoesNotExist:
                # Most probable running during syncdb phase,
                # so ignore the exception
                pass
            except DatabaseError:
                # ContentType model DB table doesn't exists,
                # raise original exception
                raise database_error
            else:
                # The ContentType model exists,
                # there is something wrong with the DB
                # raise original exception
                transaction.rollback()
                raise database_error

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I don't think there is a way to know if syncdb is running, but there is a way to handle exceptions in python:

Just catch and exception and pass:

try:
    # code that deals with django user
except ExceptionYouAreGetting:
    # seems like syncdb is running, let's pass for now
    pass

---

AFAIK it's not possible to detect whether or not syncdb is running, however, when syncdb or loaddata is running, your signals will receive an extra argument raw.

@receiver(post_save, sender=ModelA)
def signal_handler(sender, **kwargs):
    raw = kwargs.get('raw', False)
    if not raw:
        <do whatever>

This way, you can skip signals to be run when syncdb is being executed.