How to override object names in forms.ModelMultipleChoiceField in Django Admin?

Question

Django

Models:

class PostTag(models.Model):
    title = models.CharField(max_length=255)

class Post(models.Model):
    title = models.CharField(max_length=255)
    post_tag = models.ManyToManyField(PostTag, null=True, blank=True)

Admin:

class PostAdmin(ModelAdmin):
    filter_horizontal = ('post_tag',)

A list of tags is displayed, but I need to add the number of posts for this tag to the tag name. How to do this?

Answer 1

https://docs.djangoproject.com/en/1.7/ref/contrib/...
there are many examples there. In short, you create a new function for the model that returns the amount. Add allow_tags. We go to the admin panel and write lists_display. Everything.
True, I did not use manytomany. For foreign keys only.
I decided to check, everything is working fine. Only not quite the same, but the principle is clear.
models.py

from django.utils.html import format_html

class PostTag(models.Model):
    title = models.CharField(max_length=255)

    def __str__(self):
        return self.title

    def get_count_posts(self):
        return format_html('<span style="color: red">{0}</span>', self.post_set.count())

    get_count_posts.allow_tags = True

class Post(models.Model):
    title = models.CharField(max_length=255)
    post_tag = models.ManyToManyField(PostTag, null=True, blank=True)

    def __str__(self):
        return self.title

admin.py

from games.models import PostTag, Post


class PostTagAdmin(admin.ModelAdmin):
    list_display = ('title', 'get_count_posts')


admin.site.register(PostTag, PostTagAdmin)
admin.site.register(Post)