[Python] Django: show the count of related objects in admin list_display

I would like to show the count of related objects in django's list_display property. for example we have a category field and we want to show how many blog posts are posted in this category

I have tried this so far:

admin.py:

from .models import Category

class CategoryAdmin(admin.ModelAdmin):
def category_post_count(self, obj):
return obj.post_set.count
category_post_count.short_description = "Posts Count"

list_display = ['category', 'category_post_count']


models.py:

class Category(models.Model):
category = models.CharField(max_length=25)

class Post(models.Model):
category = models.ForeignKey(Category, null=True, blank=False)

Continue reading...