To connect with Cloud SQL instances from our Python code, we use the MySQLdb package, which is a MySQL driver that implements the Python Database API as described in the PEP 249 document. To install the package, we can use pip; from the command line, we issue the following command:

pip install MySQL-python

We don't specify the -t option as we did when installing GCS Client Library in Chapter 3, Storing and Processing Users' Data because the MySQLdb package is included in App Engine Python Runtime Environment on the production servers and we don't need to upload it during deployment. Instead, we list the package in the libraries section of the app.yaml file:

libraries:
- name: webapp2
  version: "2.5.2"

- name: jinja2
  version: latest

- name: MySQLdb
  version: latest

A simple test to check if the database connection is working correctly consists of retrieving and logging the Cloud SQL version number. We add a function...