python - save() でデータベースに 2 回作成されたオブジェクト

Question

これが私のクラスモデルです：

class Request(models.Model):
    client = models.ForeignKey(Client, related_name='requests')
    driver = models.ForeignKey(Driver, related_name='requests', null=True, blank=True)

    fare = models.OneToOneField(Fare, null=True, blank=True)

    REQUEST_STATE_CHOICES = ((0, 'NEW'), (1, 'PROCESSING'), (2, 'SUCCEED'), (3, 'FAILED'))
    state = models.IntegerField(choices=REQUEST_STATE_CHOICES, default=0)
    express = models.BooleanField(default=True)

    created = models.DateTimeField(default=datetime.datetime.today())
    modified = models.DateTimeField(default=datetime.datetime.today())

    request_date = models.DateTimeField(default=None, null=True, blank=True)

    origin_lat = models.FloatField(null=True, blank=True)
    origin_lon = models.FloatField(null=True, blank=True)
    origin_address = models.CharField(max_length=200, null=True, blank=True)
    destination_address = models.CharField(max_length=200, null=True, blank=True)

    NB_DRIVERS_AROUND = 10

    @staticmethod
    def createRequest(client, originLat, originLon, originAddress, destinationAddress, requestDate=None, driver=None):
        """
        Create request
        :param client: the client
        :param originLat: origin latitude
        :param originLon: origin longitude
        :param originAddress: origin address
        :param destinationAddress: destination address
        :param driver: driver, default=None
        """
        request = Request()
        request.client = client
        request.origin_lat = originLat
        request.origin_lon = originLon
        request.origin_address = originAddress
        request.destination_address = destinationAddress
        request.driver = driver
        if driver is not None:
            request.express = False

        if requestDate is None:
            request.request_date = datetime.datetime.now()
        else:
            request.request_date = requestDate

        request.save()

ビューから Request.createRequest(...) を呼び出すと、2 つのオブジェクトがデータベースに作成されます (管理者とデータベースを確認しました)。manage.py shellRequest オブジェクトを 1 つだけ介して呼び出すと、期待どおりに作成されます。私はDjango 1.6とpostgresqlを使用しています

を介した呼び出しは次のviewsとおりです。

def test(request):
    client = Client.objects.get(username='brams')

    Request.createRequest(client, 36.822718, 10.15789, 'Rue 6449, el omrane', 'le kram',   requestDate=None,driver=None)

    return render(request, 'test.html', {})

を介した呼び出しは次のmanage.py shellとおりです。

>>> from etaxi_prod.models import Request, Client
>>> Request.objects.all()
[]
>>> client = Client.objects.get(username='brams')
>>> request = Request.createRequest(client, 36.822718, 10.15789, 'Rue 6449, el omrane',     'le kram', requestDate=None, driver=None)
>>> request
<Request: Request object>
>>> Request.objects.all()
[<Request: Request object>]
>>>

なぜなのかご存知ですか？(すでに何時間もかけて Django のドキュメントと問題をチェックしましたが、何も見つかりませんでした)