Django信号对于模型值的改变情况？

# models.py
from django.db import models
from django.db.models.signals import post_save
from django.dispatch import receiver
from django.core.mail import send_mail

class Blog(models.Model):
    title = models.CharField(max_length=100)
    content = models.TextField()

@receiver(post_save, sender=Blog)
def notify_admin(sender, instance, created, **kwargs):
    if created:
        send_mail(
            'New Blog Post Created',
            f'A new blog post "{instance.title}" has been created.',
            'noreply@example.com',
            ['admin@example.com'],
            fail_silently=False,
        )

import logging

logger = logging.getLogger(__name__)

@receiver(post_save, sender=Blog)
def notify_admin(sender, instance, created, **kwargs):
    try:
        if created:
            send_mail(
                'New Blog Post Created',
                f'A new blog post "{instance.title}" has been created.',
                'noreply@example.com',
                ['admin@example.com'],
                fail_silently=False,
            )
    except Exception as e:
        logger.error(f'Failed to send email notification: {e}')