CODEWITHSUNDEEP
pythondjango
parijath
parijath

Reputation: 113

Error while loading data from fixture

I have the following model and manager.

class StateManager(models.Manager):
    def get_by_natural_key(self, name):
        return self.get(name=name)


class State(models.Model):

    class Meta:
        verbose_name = "State"
        verbose_name_plural = "States"
        permissions = (
            ('access_state', 'Can access States'),
        )

    COUNTRIES = (
        ('India', 'India'),
        ('USA', 'USA'),
        ('Thailand', 'Thailand'),
    )

    # Managers
    objects = StateManager()

    # Database fields
    name = models.CharField(
        'Name',
        max_length=100,
        unique=True,
        help_text='''
        100 chars max
        '''
    )
    code = models.CharField(
        'Code',
        max_length=10,
        unique=True,
        help_text='''
        10 chars max
        ''',
        null=True, blank=True
    )
    country = models.CharField(
        max_length=50,
        default="India",
        choices=COUNTRIES,
        blank=False,
        null=False
    )

    def __str__(self):
        return self.name

    def natural_key(self):
        return self.name

My fixture file is given below

    [
    {
        "model": "parties.state",
        "fields": {
            "name": "Andaman and Nicobar",
            "code": "AN",
            "country": "India"
        }
    },
    {
        "model": "parties.state",
        "fields": {
            "name": "Andhra Pradesh",
            "code": "AP",
            "country": "India"
        }
    },
]

I've earlier dumped the data to a fixture file. But when I am trying to load the fixture now, I am getting the following error ...

Traceback (most recent call last):
.....
.....
  TypeError: get_by_natural_key() takes 2 positional arguments but 20 were given
.....
.....

  File "/home/parijath/Projects/virtualenv/django18/lib/python3.4/site-packages/django/core/serializers/base.py", line 195, in build_instance
    obj.pk = Model._default_manager.db_manager(db).get_by_natural_key(*natural_key).pk
django.core.serializers.base.DeserializationError: Problem installing fixture '/home/parijath/Projects/django_projects/webportal18_multipleapps/parties/fixtures/states.json': get_by_natural_key() takes 2 positional arguments but 20 were given

Upvotes: 3

Views: 512

Answers (1)

Alasdair
Alasdair

Reputation: 309089

The natural_key method should return a tuple, not a string.

def natural_key(self):
    return (self.name,)

If natural_key is a string "Andaman and Nicobar" instead of a tuple ('Andaman and Nicobar',) then *natural_key will unpack each of the 19 characters in the string as a separate argument. Along with self, that gives you 20 arguments from your error message.

Upvotes: 4

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