Django Naturaltime is not working in .annotate

Question

Here I just wants to annotate a field on a model that gives human readable format saying how much time elapsed since it's created

My Model is created 30 seconds ago

My Model Description:

from django.db import models 
class MyModel(models.Model):
    name = models.CharField(max_length=100)
    created_at = models.DateTimeField(auto_now_add=True)

class Meta:
    ordering = ['-created_at']

@property
def natural_time(self):
    return naturaltime(self.created_at)

What I did is here

from django.contrib.humanize.templatetags.humanize import naturaltime
from django.db.models import F
from .models import MyModel
m = MyModel.objects.annotate(timesincecreated=naturaltime(F('created_at'))
print m.values('timesincecreated')

on this print call I am getting the DateTimeField that I used in the model. But If I want to access the property.

from .models import MyModel
m= MyModel.objects.first()
print m.natural_time

It works.

Any help? TIA.

Answer 1

You cannot use naturaltime function for annotation , annotation is a computation that is done on database level.

Django provides only a set of basic computations which can be processed by the database like Count, Sum, Min, Max , etc. You can refer to official doc to learn more about Query Expressions .