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Django library for separating the message content from transmission method

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A Django messaging library that features:

  • Class-based declaration and registry approach, like Django Admin
  • Supports multiple transmission methods (Email, SMS, Slack, etc) per message
  • Browser-based previewing of messages
  • Maintains a history of messaging sending attempts and can view these messages
  • Disabling notifications per user

Python/Django Support

We try to make herald support all versions of django that django supports + all versions in between.

For python, herald supports all versions of python that the above versions of django support.

So as of herald v0.2 we support django 1.11, 2.0, 2.1, and 2.2, and python 2.7, 3.4, 3.5, 3.6, and 3.7.

What version of herald do I need if I have django x and python x?

If the django/python version combination has a --- in the table, it is not guaranteed to be supported.

py 2.7 py 3.3 py 3.4 py 3.5 py 3.6 py 3.7
dj 1.8 <0.2 <0.2 <0.2 <0.2 --- ---
dj 1.9 - 1.10 <0.2 --- <0.2 <0.2 --- ---
dj 1.11 >=0.1.5 --- >=0.1.5 >=0.1.5 >=0.1.5 ---
dj 2.0 --- --- >=0.1.5 >=0.1.5 >=0.1.5 >=0.2
dj 2.1 --- --- --- >=0.2 >=0.2 >=0.2
dj 2.2 --- --- --- >=0.2 >=0.2 >=0.2


  1. pip install django-herald

  2. Add herald and django.contrib.sites to INSTALLED_APPS.

  3. Add herald's URLS:

    if settings.DEBUG:
        urlpatterns = [
            url(r'^herald/', include('herald.urls')),
        ] + urlpatterns


  1. Create a file in any django app. This is where your notification classes will live. Add a class like this:
from herald import registry
from herald.base import EmailNotification

class WelcomeEmail(EmailNotification):  # extend from EmailNotification for emails
    template_name = 'welcome_email'  # name of template, without extension
    subject = 'Welcome'  # subject of email

    def __init__(self, user):  # optionally customize the initialization
        self.context = {'user': user}  # set context for the template rendering
        self.to_emails = []  # set list of emails to send to

    def get_demo_args():  # define a static method to return list of args needed to initialize class for testing
        from users.models import User
        return [User.objects.order_by('?')[0]]

registry.register(WelcomeEmail)  # finally, register your notification class

# Alternatively, a class decorator can be used to register the notification:

class WelcomeEmail(EmailNotification):
  1. Create templates for rendering the email using this file structure:

  2. Test how your email looks by navigating to /herald/.

  3. Send your email wherever you need in your code:

  4. View the sent emails in django admin and even be able to resend it.

Email options

The following options can be set on the email notification class. For Example:

class WelcomeEmail(EmailNotification):
    cc = ['']
  • from_email: (str, default: settings.DEFAULT_FROM_EMAIL) email address of sender
  • subject: (str, default: ) email subject
  • to_emails: (List[str], default: None) list of email strings to send to
  • bcc: (List[str], default: None) list of email strings to send as bcc
  • cc: (List[str], default: None) list of email strings to send as cc
  • headers: (dict, default: None) extra headers to be passed along to the EmailMultiAlternatives object
  • reply_to: (List[str], default: None) list of email strings to send as the Reply-To emails
  • attachments: (list) list of attachments. See "Email Attachments" below for more info

Automatically Deleting Old Notifications

Herald can automatically delete old notifications whenever a new notification is sent.

To enable this, set the HERALD_NOTIFICATION_RETENTION_TIME setting to a timedelta instance.

For example:


Will delete all notifications older than 8 weeks every time a new notification is sent.

Manually Deleting Old Notifications

The delnotifs command is useful for purging the notification history.

The default usage will delete everything from sent during today:

python delnotifs

However, you can also pass arguments for start or end dates. end is up to, but not including that date.

python delnotifs --start='2016-01-01' --end='2016-01-10'

Asynchronous Email Sending

If you are sending slightly different emails to a large number of people, it might take quite a while to process. By default, Django will process this all synchronously. For asynchronous support, we recommend django-celery-email. It is very straightfoward to setup and integrate:


Django has built-in support for sending password reset emails. If you would like to send those emails using herald, you can use the notification class in herald.contrib.auth.

First, add herald.contrib.auth to INSTALLED_APPS (in addition to herald).

Second, use the HeraldPasswordResetForm in place of django's built in PasswordResetForm. This step is entirely dependant on your project structure, but it essentially just involves changing the form class on the password reset view in some way:

# you may simply just need to override the password reset url like so:
url(r'^password_reset/$', password_reset, name='password_reset', {'password_reset_form': HeraldPasswordResetForm}),

# of if you are using something like django-authtools:
url(r'^password_reset/$', PasswordResetView.as_view(form_class=HeraldPasswordResetForm), name='password_reset'),

# or you may have a customized version of the password reset view:
class MyPasswordResetView(FormView):
    form_class = HeraldPasswordResetForm  # change the form class here

# or, you may have a custom password reset form already. In that case, you will want to extend from the HeraldPasswordResetForm:
class MyPasswordResetForm(HeraldPasswordResetForm):

# alternatively, you could even just send the notification wherever you wish, seperate from the form:

Third, you may want to customize the templates for the email. By default, herald will use the registration/password_reset_email.html that is provided by django for both the html and text versions of the email. But you can simply override herald/html/password_reset.html and/or herald/text/password_reset.txt to suit your needs.

User Disabled Notifications

If you want to disable certain notifications per user, add a record to the UserNotification table and add notifications to the disabled_notifications many to many table.

For example:

user = User.objects.get(

notification = Notification.objects.get(notification_class=MyNotification.get_class_path())

# disable the notification

By default, notifications can be disabled. You can put can_disable = False in your notification class and the system will populate the database with this default. Your Notification class can also override the verbose_name by setting it in your inherited Notification class. Like this:

class MyNotification(EmailNotification):
    can_disable = False
    verbose_name = "My Required Notification"

Email Attachments

To send attachments, assign a list of attachments to the attachments attribute of your EmailNotification instance, or override the get_attachments() method.

Each attachment in the list can be one of the following:

  1. A tuple which consists of the filename, the raw attachment data, and the mimetype. It is up to you to get the attachment data. Like this:
raw_data = get_pdf_data()

email.attachments = [
    ('Report.pdf', raw_data, 'application/pdf'),
    ('report.txt', 'text version of report', 'text/plain')
  1. A MIMEBase object. See the documentation for attachments under EmailMessage Objects/attachments in the Django documentation.

  2. A django File object.

Inline Attachments

Sometimes you want to embed an image directly into the email content. Do that by using a MIMEImage assigning a content id header to a MIMEImage, like this:

email = WelcomeEmail(user)
im = get_thumbnail(, '600x600', quality=95)
my_image = MIMEImage( # MIMEImage inherits from MIMEBase
my_image.add_header('Content-ID', '<{}>'.format(

You can refer to these images in your html email templates using the Content ID (cid) like this:

<img src="cid:{{}}" />

You would of course need to add the "image_file" to your template context in the example above. You can also accomplish this using file operations. In this example we overrode the get_attachments method of an EmailNotification.

class MyNotification(EmailNotification):
    context = {'hello': 'world'}
    template_name = 'welcome_email'
    to_emails = ['']
    subject = "My email test"

    def get_attachments(self):
        fp = open('python.jpeg', 'rb')
        img = MIMEImage(
        img.add_header('Content-ID', '<{}>'.format('python.jpeg'))
        return [

And in your template you would refer to it like this, and you would not need to add anything to the context:

    <img src="cid:python.jpeg" />

Other MIME attachments

You can also attach any MIMEBase objects as regular attachments, but you must add a content-disposition header, or they will be inaccessible:

my_image.add_header('Content-Disposition', 'attachment; filename="python.jpg"')

Attachments can cause your database to become quite large, so you should be sure to run the management commands to purge the database of old messages.

Running Tests


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