Calling PL/SQL Stored Functions in Python

Summary: in this tutorial, you will learn how to use the Cursor.callfunc() to call a PL/SQL stored function from a Python program.

Setting up a PL/SQL function

The following statement creates a new stored function called get_revenue() that returns the sales revenue by a salesman in a specific year.

CREATE OR REPLACE FUNCTION get_revenue(
    salesman_code NUMBER,
    year NUMBER)
RETURN NUMBER
IS
    l_revenue NUMBER;
BEGIN
    SELECT 
        SUM(quantity*unit_price)
    INTO l_revenue
    FROM 
        orders
    INNER JOIN 
        order_items USING (order_id)
    WHERE 
        salesman_id = salesman_code AND 
        EXTRACT(YEAR FROM order_date) = YEAR;
    RETURN l_revenue;
END;          

This anonymous block tests the stored function get_revenue() that get the sales revenue of the salesman id 54 in the year 2017:

SET SERVEROUTPUT ON;

DECLARE
    l_revenue NUMBER;
BEGIN
    l_revenue := get_revenue(54, 2017);
    dbms_output.put_line(l_revenue);
END;    

Here is the output:

1160350.79

Calling a PL/SQL stored function example

To execute a PL/SQL stored function, you use the Cursor.callproc() method. The following code illustrates how to call the stored function get_revenue() and display the revenue of salesman 54 in the year 2017:

import cx_Oracle
import config as cfg


def get_revenue(salesman_id, year):
    """
    Get revenue by salesman in a specific year
    :param salesman_id:
    :param year:
    :return: the revenue
    """
    revenue = None
    try:
        # create a connection to the Oracle Database
        with cx_Oracle.connect(cfg.username,
                            cfg.password,
                            cfg.dsn,
                            encoding=cfg.encoding) as connection:
            # create a new cursor
            with connection.cursor() as cursor:
                # call the function
                revenue = cursor.callfunc('get_revenue',
                                        float,
                                        [salesman_id, year])
    except cx_Oracle.Error as error:
        print(error)

    return revenue


if __name__ == '__main__':
    sales_revenue = get_revenue(54, 2017)
    print(sales_revenue)  # 1160350.79

In this example:

First, establish a connection to the Oracle Database by calling the cx_Oracle.connect() method with the parameters provided by the config module:

username = 'OT'
password = '<password>'
dsn = 'localhost/pdborcl'
port = 1512
encoding = 'UTF-8'

Second, create a new Cursor object using the Connection.cursor() method.

Third, call the stored function get_revenue() using the Cursor.callfunc() method:

cursor.callfunc('get_revenue', float, [salesman_id, year])

In the Cursor.callfunc() method: the first argument is the stored function’s name, the second argument is the type of the returned value, and the third argument is a list of arguments passed to the stored function.

The following code tests the get_revenue() function with the salesman 54 and the year 2017:

sales_revenue = get_revenue(54, 2017)
print(sales_revenue)  # 1160350.79

In this tutorial, you have learned how to use the Cursor.callfunc() method to call a PL/SQL stored function in Python.