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MariaDB is an open source version of the popular MySQL relational database management system (DBMS) with a SQL interface for accessing and managing data. It is highly reliable and easy to administer, which are essential qualities of a DBMS capable of serving modern applications. With Python’s growing popularity in technologies like artificial intelligence and machine learning, MariaDB makes a good option for a database server for Python.
In this tutorial, you will connect a Python application to a database server using the MySQL connector. This module allows you to make queries on the database server from within your application. You’ll set up MariaDB for a Python environment on Ubuntu 18.04 and write a Python script that connects to and executes queries on MariaDB.
Before you begin this guide, you will need the following:
In this step, you’ll create a database and a table in MariaDB.
First, open your terminal and enter the MariaDB shell from the terminal with the following command:
- sudo mysql
Once you’re in the MariaDB shell, your terminal prompt will change. In this tutorial, you’ll write Python to connect to an example employee database named workplace
and a table named employees
.
Start by creating the workplace
database:
- CREATE DATABASE workplace;
Next, tell MariaDB to use workplace
as your current database:
- USE workplace;
You will receive the following output, which means that every query you run after this will take effect in the workplace
database:
OutputDatabase changed
Next, create the employees
table:
- CREATE TABLE employees (first_name CHAR(35), last_name CHAR(35));
In the table schema, the parameters first_name
and a last_name
are specified as character strings (CHAR
) with a maximum length of 35
.
Following this, exit the MariaDB shell:
- exit;
Back in the terminal, export your MariaDB authorization credentials as environment variables:
- export username="username"
- export password="password"
This technique allows you to avoid adding credentials in plain text within your script.
You’ve set up your environment for the project. Next, you’ll begin writing your script and connect to your database.
In this step, you will install the MySQL Connector and set up the database.
In your terminal, run the following command to install the Connector:
- pip3 install mysql-connector-python
pip
is the standard package manager for Python. mysql-connector-python
is the database connector Python module.
Once you’ve successfully installed the connector, create and open a new file Python file:
- nano database.py
In the opened file, import the os
module and the mysql.connector
module using the import
keyword:
import os
import mysql.connector as database
The as
keyword here means that mysql.connector
will be referenced as database
in the rest of the code.
Next, initialize the authorization credentials you exported as Python variables:
. . .
username = os.environ.get("username")
password = os.environ.get("password")
Follow up and establish a database connection using the connect()
method provided by database
. The method takes a series of named arguments specifying your client credentials:
. . .
connection = database.connect(
user=username,
password=password,
host=localhost,
database="workplace")
You declare a variable named connection
that holds the call to the database.connect()
method. Inside the method, you assign values to the user
, password
, host
, and database
arguments. For user and password, you will reference your MariaDB authorization credentials. The host will be localhost
by default if you are running the database on the same system.
Lastly, call the cursor()
method on the connection to obtain the database cursor:
. . .
cursor = connection.cursor()
A cursor is a database object that retrieves and also updates data, one row at a time, from a set of data.
Leave your file open for the next step.
Now you can connect to MariaDB with your credentials; next, you will add entries to your database using your script.
Using the execute()
method on the database cursor, you will add entries to your database in this step.
Define a function add_data()
to accept the first and last names of an employee as arguments. Inside the function, create a try/except block. Add the following code following your cursor object:
. . .
def add_data(first_name, last_name):
try:
statement = "INSERT INTO employees (first_name,last_name) VALUES (%s, %s)"
data = (first_name, last_name)
cursor.execute(statement, data)
connection.commit()
print("Successfully added entry to database")
except database.Error as e:
print(f"Error adding entry to database: {e}")
You use the try
and except
block to catch and handle exceptions (events or errors) that disrupt the normal flow of program execution.
Under the try
block, you declare statement
as a variable holding your INSERT
SQL statement. The statement tells MariaDB to add to the columns first_name
and last_name
.
The code syntax accepts data as parameters that reduce the chances of SQL injection. Prepared statements with parameters ensure that only given parameters are securely passed to the database as intended. Parameters are generally not injectable.
Next you declare data
as a tuple with the arguments received from the add_data
function. Proceed to run the execute()
method on your cursor
object by passing the SQL statement and the data. After calling the execute()
method, you call the commit()
method on the connection to permanently save the inserted data.
Finally, you print out a success message if this succeeds.
In the except
block, which only executes when there’s an exception, you declare database.Error
as e
. This variable will hold information about the type of exception or what event happened when the script breaks. You then proceed to print out an error message formatted with e
to end the block using an f-string.
After adding data to the database, you’ll next want to retrieve it. The next step will take you through the process of retrieving data.
In this step, you will write a SQL query within your Python code to retrieve data from your database.
Using the same execute()
method on the database cursor, you can retrieve a database entry.
Define a function get_data()
to accept the last name of an employee as an argument, which you will call with the execute()
method with the SELECT
SQL query to locate the exact row:
. . .
def get_data(last_name):
try:
statement = "SELECT first_name, last_name FROM employees WHERE last_name=%s"
data = (last_name,)
cursor.execute(statement, data)
for (first_name, last_name) in cursor:
print(f"Successfully retrieved {first_name}, {last_name}")
except database.Error as e:
print(f"Error retrieving entry from database: {e}")
Under the try
block, you declare statement
as a variable holding your SELECT
SQL statement. The statement tells MariaDB to retrieve the columns first_name
and last_name
from the employees
table when a specific last name is matched.
Again, you use parameters to reduce the chances of SQL injection.
Smilarly to the last function, you declare data
as a tuple with last_name
followed by a comma. Proceed to run the execute()
method on the cursor
object by passing the SQL statement and the data. Using a for
loop, you iterate through the returned elements in the cursor and then print out if there are any successful matches.
In the except
block, which only executes when there is an exception, declare database.Error
as e
. This variable will hold information about the type of exception that occurs. You then proceed to print out an error message formatted with e
to end the block.
In the final step, you will execute your script by calling the defined functions.
In this step, you will write the final piece of code to make your script executable and run it from your terminal.
Complete your script by calling add_data()
and get_data()
with sample data (strings) to verify that your code is working as expected.
If you would like to add multiple entries, you can call add_data()
with further sample names of your choice.
Once you finish working with the database make sure that you close the connection to avoid wasting resources:
connection.close()
:
import os
import mysql.connector as database
username = os.environ.get("username")
password = os.environ.get("password")
connection = database.connect(
user=username,
password=password,
host=localhost,
database="workplace")
cursor = connection.cursor()
def add_data(first_name, last_name):
try:
statement = "INSERT INTO employees (first_name,last_name) VALUES (%s, %s)"
data = (first_name, last_name)
cursor.execute(statement, data)
cursor.commit()
print("Successfully added entry to database")
except database.Error as e:
print(f"Error adding entry to database: {e}")
def get_data(last_name):
try:
statement = "SELECT first_name, last_name FROM employees WHERE last_name=%s"
data = (last_name,)
cursor.execute(statement, data)
for (first_name, last_name) in cursor:
print(f"Successfully retrieved {first_name}, {last_name}")
except database.Error as e:
print(f"Error retrieving entry from database: {e}")
add_data("Kofi", "Doe")
get_data("Doe")
connection.close()
Make sure you have indented your code correctly to avoid errors.
In the same directory, you created the database.py
file, run your script with:
- python3 ./database.py
You will receive the following output:
OutputSuccessfully added entry to database
Successfully retrieved Kofi, Doe
Finally, return to MariaDB to confirm you have successfully added your entries.
Open up the MariaDB prompt from your terminal:
- sudo mysql
Next, tell MariaDB to switch to and use the workplace
database:
- USE workplace;
After you get the success message Database changed
, proceed to query for all entries in the employees
table:
- SELECT * FROM employees;
You output will be similar to the following:
Output+------------+-----------+
| first_name | last_name |
+------------+-----------+
| Kofi | Doe |
+------------+-----------+
1 row in set (0.00 sec)
Putting it all together, you’ve written a script that saves and retrieves information from a MariaDB database.
You started by importing the necessary libraries. You used mysql-connector
to connect to the database and os
to retrieve authorization credentials from the environment. On the database connection, you retrieved the cursor to carry out queries and structured your code into add_data
and get_data
functions. With your functions, you inserted data into and retrieved data from the database.
If you wish to implement deletion, you can build a similar function with the necessary declarations, statements, and calls.
You have successfully set up a database connection to MariaDB using a Python script on Ubuntu 18.04. From here, you could use similar code in any of your Python projects in which you need to store data in a database. This guide may also be helpful for other relational databases that were developed out of MySQL.
For more on how to accomplish your projects with Python, check out other community tutorials on Python.
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