Build a Python Application

To build a Python application that accesses an Autonomous AI Database, you start by configuring your development system to support database access that can take advantage of the continuous availability and high performance features of Autonomous AI Database.

After configuring your development system, you code database connections and SQL statements in your application to take advantage of these features.

Tip: For a “try it out” alternative to reading the following topics, you can go through the Lab 4: Build Python Application Stacks in Oracle Autonomous AI Database Dedicated for Developers and Database Users Workshop.

Configure Your Python Development System

To configure your development system so that your Python application can take advantage of the continuous availability and high performance features of an Autonomous AI Database, you perform these steps.

Download and install Python.
Download and install Oracle Instant Client.
Download and install cx_Oracle.
Download the client credentials for the database and make them available to Oracle Instant Client.

Before You Begin

Your development system must meet certain criteria to configure it successfully.

It must have internet access.
It must have network access to the Autonomous AI Database.

See Configure a Development System to Access the Database to learn how to ensure your development system meets this requirement.

Download and Install Python

Oracle Linux:

Oracle Linux 7 includes Python 2.7, so you simply run this command::
```
sudo yum -y install oracle-release-el7
```
Other OSes and architectures:

Go to the python.org Downloads page and download and install the latest Python 2.7 or Python 3.5 (or later) version for your OS and architecture.

Download and Install Oracle Instant Client

You need Oracle Instant Client libraries version 19.6 or later.

Download and install the Oracle Instant Client basic package for your system’s OS and architecture:

Oracle Linux:

Run these commands to download and install the Oracle Instant Client basic package:
```
sudo yum -y install oracle-release-el7
sudo yum -y install oracle-instantclient19.3-basic
```
(If you want to see a list of all Instant Client packages, go to http://yum.oracle.com/repo/OracleLinux/OL7/oracle/instantclient/x86_64/index.html.)
Other OSes and architectures:
1. Go to the Oracle Instant Client Downloads page and select the download for your system's OS and architecture.
2. On the download page, accept the Oracle Technology Network License Agreement, download the latest version of the Basic Package, and then install it by following the instructions at the bottom of the download page.

Download and Install cx_Oracle

Use Python’s pip package to install cx_Oracle from PyPI (the Python Package Index).:

Oracle Linux:

Run these commands to download the pip package and then use it to install cx_Oracle:

sudo yum -y install oracle-release-el7
curl https://bootstrap.pypa.io/get-pip.py -o get-pip.py
sudo python get-pip.py
python -m pip install cx_Oracle --upgrade

Other OSes and architectures:

Run this command:
```
python -m pip install cx_Oracle --upgrade
```

Download and Install Client Credentials for the Database

Download the zip file containing client credentials for your database to a secure directory on your computer.

This zip file is available for download from the database's Details page in the Oracle Cloud console. If you have an Oracle Cloud user account that permits you to access this page, download the credentials as follows. If you don't have such an account, you need to get the zip file from the administrator of the database, together with the password that was used to protect the zip file.
1. In your web browser, sign in to Oracle Cloud and navigate to the Details page for the Autonomous AI Database.
2. Click DB Connection.
3. On the Database Connection page click Download.
4. In the Download Wallet dialog, enter a wallet password in the Password field and confirm the password in the Confirm Password field.
  
  The password must be at least 8 characters long and must include at least 1 letter and either 1 numeric character or 1 special character.
5. Click Download to save the client credentials zip file to a secure directory.
After downloading the zip file, follow these steps:
1. Unzip the client credentials zip file.
2. Edit the sqlnet.ora file provided in the client credentials, replacing "?/network/admin" with the full path of the directory where you unzipped the client credentials; for example, change:
```
 (DIRECTORY="?/network/admin")
```
  to
```
 (DIRECTORY="/users/jdoe/adbcredentials")
```
3. Create the TNS_ADMIN environment variable, setting its value to the full path of the directory where you unzipped the client credentials.

Code Database Connections and SQL Statements

After configuring your development system to support Python application connectivity to an Autonomous AI Database, follow these guidelines to achieve high performance and continuous availability of your application’s connections to the database:

Use connection pools.
Enable FAN (Fast Application Notification).
Use the predefined database service that best matches the operations you will be performing. For information about the predefined database services, see Predefined Database Service Names for Autonomous AI Database.

For example:

pool = cx_Oracle.SessionPool("appuser",
                             SampleEnv.GetMainPassword(),
                             "tp_tls",
                             events=True,
                             threaded=True)

This example creates a pool for connections to the tp_tls database service, and enables FAN by setting the events parameter to True.