How to Incorporate Custom Configuration in a Pyramid Application

Note: This post shows an old way to modify the request object. I discuss a new way in my Pyramid add_request_method post.

Imagine that you have just built a wiki, blog, or cms web application that will be deployed multiple times by different people. You would like to provide the ability to configure some aspects of the program without the end user altering your python or template code. This guide explains how to incorporate custom configuration from the project's .ini file with the rest of the application.

To explain this process we will add a customizable Google Analytics key to our project.

1. Make a configuration key/value pair for Google Analytics
2. Add the Google Analytics javascript code to the template

Make a configuration key/value pair for Google Analytics

Inside production.ini place the following in the [app:main] section:

#google_analytics_key = UA-55555555-1
google_analytics_key =

Add the Google Analytics javascript code to the template

In this case I will show an example in mako. Other template solutions should look similar.

<%def name="google\_analytics()">
% if request.registry.settings['google_analytics_key']:


 <script type="text/javascript"></p>
 <p>var _gaq = _gaq || [];<br />
           _gaq.push(['_setAccount', "${request.registry.settings['google_analytics_key']}"]);<br />
           _gaq.push(['_trackPageview']);</p>
 <p>(function() {<br />
           var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true;<br />
           ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'https://www') + '.google-analytics.com/ga.js';<br />
           var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s);<br />
           })();</p>
 <p></script>

% endif

Then in the head section call the function:

${ google_analytics() }

That was easy because the configuration string just needed to be substituted into the JavaScript in the template. What if you needed to do something with the provided key/value before using it? Next I will show you a method for building renderer globals again showing a different way to configure Google Analytics:

Make an inject_renderer_globals subscriber

Define inject_renderer_globals(event) function in the project's __init__.py file.

I normally place it at the bottom of the file and it looks like this:

def inject_renderer_globals(event):
    """Inject some renderer globals before passing to template"""

    request = event['request']

    # Build ${google_analytics_key} from the configuration file
    event['google_analytics_key'] = request.registry.settings[ 'google_analytics_key' ]

Import BeforeRender at the top of the __init__.py:

from pyramid.events import BeforeRender

In the main function, add the inject_renderer_globals to the subscribers:

config.add_subscriber(inject_renderer_globals, BeforeRender)

Now you can use ${google_analytics_key} anywhere in your template.

Thank you for reading, and feel free to leave comments