tmp.py

tmp.py

class Degree(models.Model):

    class Meta:
        ordering = ['-popularity']
        order_with_respect_to = 'subcategories'

    name = models.CharField(unique=True, max_length=20)
    description = models.TextField(blank=True)
    popularity = models.PositiveIntegerField(default=0)
    alias_of = models.ForeignKey('self', related_name='synonyms', blank=True,
                                 null=True, limit_choices_to={'alias_of': None})
    subcategories = models.ManyToManyField('core.Subcategory', blank=True,
                                           related_name='degrees')

    def __str__(self):
        return self.name


>>> from accounts.models import Degree
>>> d = Degree(name="Foobar",  popularity=0)
>>> d.save()
Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "/home/tony/.virtualenvs/aladompy/lib/python3.3/site-packages/django/db/models/base.py", line 710, in save
    force_update=force_update, update_fields=update_fields)
  File "/home/tony/.virtualenvs/aladompy/lib/python3.3/site-packages/django/db/models/base.py", line 738, in save_base
    updated = self._save_table(raw, cls, force_insert, force_update, using, update_fields)
  File "/home/tony/.virtualenvs/aladompy/lib/python3.3/site-packages/django/db/models/base.py", line 814, in _save_table
    **{field.name: getattr(self, field.attname)}).count()
  File "/home/tony/.virtualenvs/aladompy/lib/python3.3/site-packages/django/db/models/fields/related.py", line 1242, in __get__
    through=self.field.rel.through,
  File "/home/tony/.virtualenvs/aladompy/lib/python3.3/site-packages/django/db/models/fields/related.py", line 874, in __init__
    (instance, source_field_name))
ValueError: "<Degree: Foobar>" needs to have a value for field "degree" before this many-to-many relationship can be used.