django dynamic related name on FK model inhertiance

Question

I am trying to set a class attribute dynamically, by performing an operation on another class attribute. My code goes like this

class LastActionModel(BaseModel):
    """
    Provides created_by updated_by fields if you have an instance of user,
    you can get all the items, with Item being the model name, created or updated
    by user using user.created_items() or user.updated_items()
    """
    created_by = models.ForeignKey(
        settings.AUTH_USER_MODEL, blank=True, null=True,
        related_name = lambda self:'%s_%s' %('created', \
            self._meta.verbose_name_plural.title().lower())
    )
    updated_by = models.ForeignKey(
        settings.AUTH_USER_MODEL, blank=True, null=True,
        related_name = lambda self:'%s_%s' %('updated', \
            self._meta.verbose_name_plural.title().lower())
    )

    class Meta:
        abstract = True

This is to dynamically set the related name so that for a class Item, and a User 'user', i can easily call user.created_items.all().

This is giving me the error

super(ForeignObject, self).contribute_to_class(cls, name, virtual_only=virtual_only)
    File "/home/pywebapp/venv/local/lib/python2.7/site-packages/django/db/models/fields/related.py", line 113, in contribute_to_class
        'app_label': cls._meta.app_label.lower()
TypeError: Error when calling the metaclass bases
    unsupported operand type(s) for %: 'function' and 'dict'

where i am going wrong?

Answer 1

the answer was pretty simple, as per docs

class LastActionModel(BaseModel):
    """
    Provides created_by updated_by fields if you have an instance of user,
    you can get all the items, with Item being the model name, created or updated
    by user using user.created_items() or user.updated_items()
    """
    created_by = models.ForeignKey(
        'users.User', blank=True, null=True,
        related_name = 'created_%(class)ss'
    )
    updated_by = models.ForeignKey(
        'users.User', blank=True, null=True,
        related_name = 'updated_%(class)ss'
    )

    class Meta:
        abstract = True

hope it helps