Installing the API
You can get the source from https://github.com/piwik/piwik-python-api or install it with pip:
pip install piwikapi
On Python 2.5 you'll also have to install simplejson.
To install Piwik please see http://piwik.org/docs/installation-optimization/.
Enabling the tracking API
For simple tracking you don't need to do anything. However, by default all tracking requests will originate from your server.
If you want your user's IP to be logged (you probably do) create a new user and make that user an admin of the site you want to track.
Keep in mind that the auth token will be submitted with each request, so you should consider using SSL to submit the data to your server.
Enabling ecommerce tracking
You need to enable ecommerce tracking inside Piwik, see http://piwik.org/docs/ecommerce-analytics/#toc-enable-ecommerce-for-the-website
See also :ref:`enable_tracking`.
If you want to track goals you'll have to create them first. Either through the web interface or the API.
Enabling the analytics API
The analytics API works out of the box, no configuration is needed. To view reports the viewer must have access. You could just give anonymous access to the data but it's probably better to use the auth token.
Secure your install
First you should check the official docs at http://piwik.org/security/how-to-secure-piwik/.
If you use the Python API exclusively you could consider password-protecting your Piwik install or binding the httpd to local interfaces only etc.