python 39 lines · 8 steps

Sending a welcome email with Django signals

A post_save signal fires a multipart activation email whenever a new user is created.

Explained by highlit
Django Intermediate signals email user-activation templates event-driven
1from django.conf import settings
2from django.contrib.auth import get_user_model
3from django.core.mail import EmailMultiAlternatives
4from django.db.models.signals import post_save
5from django.dispatch import receiver
6from django.template.loader import render_to_string
7from django.urls import reverse
8from django.utils.encoding import force_bytes
9from django.utils.http import urlsafe_base64_encode
10 
11User = get_user_model()
12 
13 
14@receiver(post_save, sender=User, dispatch_uid="send_welcome_email")
15def send_welcome_email(sender, instance, created, **kwargs):
16 if not created or not instance.email:
17 return
18 
19 uid = urlsafe_base64_encode(force_bytes(instance.pk))
20 activation_path = reverse("accounts:activate", kwargs={"uidb64": uid, "token": instance.activation_token})
21 context = {
22 "user": instance,
23 "activation_url": settings.SITE_URL + activation_path,
24 "support_email": settings.SUPPORT_EMAIL,
25 }
26 
27 subject = "Welcome to Acme \u2014 confirm your email"
28 text_body = render_to_string("emails/welcome.txt", context)
29 html_body = render_to_string("emails/welcome.html", context)
30 
31 message = EmailMultiAlternatives(
32 subject=subject,
33 body=text_body,
34 from_email=settings.DEFAULT_FROM_EMAIL,
35 to=[instance.email],
36 reply_to=[settings.SUPPORT_EMAIL],
37 )
38 message.attach_alternative(html_body, "text/html")
39 message.send(fail_silently=False)
01 / 01
STEP 01

Walkthrough

Space play ←→ step click any line
Three takeaways
  1. 1Django signals let you hook side effects onto model lifecycle events without touching the save logic.
  2. 2Guarding on the created flag ensures the handler runs once on creation, not on every update.
  3. 3EmailMultiAlternatives sends both plain-text and HTML bodies so clients render whichever they support.

Related explainers

python 
from fastapi import APIRouter, BackgroundTasks, Depends, HTTPException, status
from pydantic import BaseModel, EmailStr
from sqlalchemy.orm import Session
 

Building a signup endpoint in FastAPI

dependency-injection request-validation background-tasks
Intermediate 8 steps
python 
from django import forms
from django.utils import timezone
 
from .models import Reservation

Multi-field validation in a Django ModelForm

form validation cross-field validation modelform
Intermediate 7 steps
python 
from django import template
from django.urls import reverse, NoReverseMatch
from django.utils.html import format_html
 

Active nav-link template tags in Django

template tags url routing active state
Intermediate 7 steps
python 
from functools import wraps
import asyncio
 
from fastapi import APIRouter, FastAPI, Request

Per-route request timeouts in FastAPI

decorators async timeouts
Intermediate 6 steps
python 
import os
from pathlib import Path
 
BASE_DIR = Path(__file__).resolve().parent.parent.parent

How a Django settings module is wired

configuration environment-variables middleware
Intermediate 8 steps
python 
def is_valid_card_number(number: str) -> bool:
    digits = [int(c) for c in number if c.isdigit()]
 
    if len(digits) < 13 or len(digits) > 19:

Validating card numbers with the Luhn check

checksum validation luhn-algorithm
Intermediate 6 steps

Share this explainer

Here's the card — post it anywhere.

Sending a welcome email with Django signals — share card
Made with highlit — turn any snippet into a walkthrough like this in about a minute.
Explain your code