@signalcommand
    @custom_transaction
    def handle(self, *fixture_labels, **options):
        """ Main method of a Django command """
        from django.db.models import get_apps
        from django.core import serializers
        from django.conf import settings

        self.style = no_style()

        verbosity = int(options.get('verbosity', 1))
        show_traceback = options.get('traceback', False)

        # Keep a count of the installed objects and fixtures
        fixture_count = 0
        object_count = 0
        objects_per_fixture = []
        models = set()

        humanize = lambda dirname: dirname and "'%s'" % dirname or 'absolute path'

        # Get a cursor (even though we don't need one yet). This has
        # the side effect of initializing the test database (if
        # it isn't already initialized).
        cursor = connection.cursor()

        app_fixtures = [os.path.join(os.path.dirname(app.__file__), 'fixtures') for app in get_apps()]
        for fixture_label in fixture_labels:
            parts = fixture_label.split('.')
            if len(parts) == 1:
                fixture_name = fixture_label
                formats = serializers.get_public_serializer_formats()
            else:
                fixture_name, format = '.'.join(parts[:-1]), parts[-1]
                if format in serializers.get_public_serializer_formats():
                    formats = [format]
                else:
                    formats = []

            if formats:
                if verbosity > 1:
                    print("Loading '%s' fixtures..." % fixture_name)
            else:
                sys.stderr.write(self.style.ERROR("Problem installing fixture '%s': %s is not a known serialization format." % (fixture_name, format)))
                transaction.rollback()
                return

            if os.path.isabs(fixture_name):
                fixture_dirs = [fixture_name]
            else:
                fixture_dirs = app_fixtures + list(settings.FIXTURE_DIRS) + ['']

            for fixture_dir in fixture_dirs:
                if verbosity > 1:
                    print("Checking %s for fixtures..." % humanize(fixture_dir))

                label_found = False
                for format in formats:
                    if verbosity > 1:
                        print("Trying %s for %s fixture '%s'..." % (humanize(fixture_dir), format, fixture_name))
                    try:
                        full_path = os.path.join(fixture_dir, '.'.join([fixture_name, format]))
                        fixture = open(full_path, 'r')
                        if label_found:
                            fixture.close()
                            print(self.style.ERROR("Multiple fixtures named '%s' in %s. Aborting." % (fixture_name, humanize(fixture_dir))))
                            transaction.rollback()
                            return
                        else:
                            fixture_count += 1
                            objects_per_fixture.append(0)
                            if verbosity > 0:
                                print("Installing %s fixture '%s' from %s." % (format, fixture_name, humanize(fixture_dir)))
                            try:
                                objects_to_keep = {}
                                objects = serializers.deserialize(format, fixture)
                                for obj in objects:
                                    object_count += 1
                                    objects_per_fixture[-1] += 1

                                    class_ = obj.object.__class__
                                    if class_ not in objects_to_keep:
                                        objects_to_keep[class_] = set()
                                    objects_to_keep[class_].add(obj.object)

                                    models.add(class_)
                                    obj.save()

                                if options.get('remove'):
                                    self.remove_objects_not_in(objects_to_keep, verbosity)

                                label_found = True
                            except (__HOLE__, KeyboardInterrupt):
                                raise
                            except Exception:
                                import traceback
                                fixture.close()
                                transaction.rollback()
                                if show_traceback:
                                    traceback.print_exc()
                                else:
                                    sys.stderr.write(self.style.ERROR("Problem installing fixture '%s': %s\n" % (full_path, traceback.format_exc())))
                                return
                            fixture.close()
                    except:
                        if verbosity > 1:
                            print("No %s fixture '%s' in %s." % (format, fixture_name, humanize(fixture_dir)))

        # If any of the fixtures we loaded contain 0 objects, assume that an
        # error was encountered during fixture loading.
        if 0 in objects_per_fixture:
            sys.stderr.write(
                self.style.ERROR("No fixture data found for '%s'. (File format may be invalid.)" % fixture_name))
            transaction.rollback()
            return

        # If we found even one object in a fixture, we need to reset the
        # database sequences.
        if object_count > 0:
            sequence_sql = connection.ops.sequence_reset_sql(self.style, models)
            if sequence_sql:
                if verbosity > 1:
                    print("Resetting sequences")
                for line in sequence_sql:
                    cursor.execute(line)

        transaction.commit()

        if object_count == 0:
            if verbosity > 1:
                print("No fixtures found.")
        else:
            if verbosity > 0:
                print("Installed %d object(s) from %d fixture(s)" % (object_count, fixture_count))

        # Close the DB connection. This is required as a workaround for an
        # edge case in MySQL: if the same connection is used to
        # create tables, load data, and query, the query can return
        # incorrect results. See Django #7572, MySQL #37735.
        connection.close()
dataset/ETHPy150Open django-extensions/django-extensions/django_extensions/management/commands/syncdata.py/Command.handle