Send HTML email in Appengine [PYTHON] using HTML file

Question

I want to send a HTML email to the users after they signup to the website. Earlier I wrote this script to send ``` from google.appengine.api import mail message = mail.EmailMessage(sender="Example.com Support ", subject="Your account has been approved") message.to = "Albert Johnson " message.body = """ Dear Albert: Your example.com account has been approved. You can now visit http://www.example.com/ and sign in using your Google Account to access new features. Please let us know if you have any questions. The example.com Team """ message.html = """ Dear Albert: Your example.com account has been approved. You can now visit http://www.example.com/ and sign in using your Google Account to access new features. Please let us know if you have any questions. The example.com Team """ message.send() ``` But instead of placing the HTML directly in the main code, I want to have a separate HTML file which wo…

Accepted Answer

Probably the best way to do this would be to use a templating engine to load and generate the HTML as a string from the HTML file. For example, if you use the webapp2 jinja2 extras package, you could do something along the lines of:

```
from webapp2_extras import jinja2 as webapp_extras_jinja2
# ...

def get_message_html():
  jinja2 = webapp_extras_jinja2.get_jinja2()
  return jinja2.render_template('relative/path/to/template.html')

# ...
def send_email():
   # ...
   message.html = get_message_html()
   # ...
```

Note that to get this working, you need to add jinja2 to the libraries section of app.yaml as in:

```
libraries:
- name: webapp2
  version: 2.5.2
- name: jinja2
  version: 2.6
```

... and you also need to include an appropriate 'webapp2_extras.jinja2' to the app config. Ex:

```
config = {
   'webapp2_extras.jinja2': {
     'template_path': 'path/containing/my/templates',
     'environment_args': {
       # Keep generated HTML short
       'trim_blocks': True,
       'extensions': [
         # Support auto-escaping for security
         'jinja2.ext.autoescape',
         # Handy but might not be needed for you
         'jinja2.ext.with_'
         # ... other extensions? ...
       ],
       # Auto-escape by default for security
       'autoescape': True
     },
     # .. other configuration options for jinja2 ...
   },
   # ... other configuration for the app ...
},
# ...
app = webapp2.WSGIApplication(routes, is_debug_enabled, config)
```

While you can just as easily open the HTML file yourself, the benefit of using a templating engine such as jinja2 is that it will encourage you to compose and reuse the HTML in a more sane way (whereas simply loading the HTML file might result in you eventually applying substitutions by hand). Also, just a quick security reminder: if any of the data you include in the email comes from untrusted sources (like the user or another user), make sure to properly validate and sanity-check the content (and also enable auto-escaping in the templating engine).

You can obviously choose a templating other than jinja2, but I specifically chose that one for my answer since it is well supported and well documented for App Engine.

Send HTML email in Appengine [PYTHON] using HTML file

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