How do you connect to a database in Python?
Jul 10, 2025 pm 01:44 PM
To connect to a database in Python, use the appropriate library for the database type. 1. For SQLite, use sqlite3 with connect() and manage with cursor and commit. 2. For MySQL, install mysql-connector-python and provide credentials in connect(). 3. For PostgreSQL, install psycopg2 and configure connection parameters including SSL if needed. 4. Optionally, use SQLAlchemy ORM for abstraction across databases by defining models and using create_engine(). Always close connections and avoid SQL injection by using parameterized queries.
Connecting to a database in Python is pretty straightforward once you know which type of database you're working with. Most common databases—like MySQL, PostgreSQL, SQLite, or MongoDB—have corresponding Python libraries that handle the connection process.
Here’s how to do it for a few popular ones.
Using SQLite with sqlite3
SQLite is built into Python, so no extra installation is needed. It's great for small apps or local development.
To connect:
import sqlite3
conn = sqlite3.connect('example.db')
cursor = conn.cursor()This creates a file-based database called example.db (or opens it if it already exists). You can then run SQL queries using the cursor object.
If you want to create a table:
cursor.execute('''CREATE TABLE IF NOT EXISTS users
(id INTEGER PRIMARY KEY, name TEXT, age INTEGER)''')
conn.commit()Don’t forget to close the connection when you’re done:
conn.close()
A couple things to watch out for:
- Always call
.commit()after making changes. - Use parameterized queries instead of string formatting to avoid SQL injection.
Connecting to MySQL with mysql-connector-python
For MySQL, you’ll need to install a package first:
pip install mysql-connector-python
Then connect like this:
import mysql.connector
conn = mysql.connector.connect(
host="localhost",
user="your_username",
password="your_password",
database="your_database"
)
cursor = conn.cursor()You can also run queries just like with SQLite:
cursor.execute("SELECT * FROM users")
results = cursor.fetchall()
for row in results:
print(row)Common issues:
- Make sure your MySQL server is running.
- Double-check credentials and permissions.
- Close the cursor and connection properly.
Working with PostgreSQL via psycopg2
PostgreSQL support comes through the psycopg2 library:
Install it first:
pip install psycopg2
Then connect:
import psycopg2
conn = psycopg2.connect(
dbname="your_db",
user="your_user",
password="your_pass",
host="localhost"
)
cursor = conn.cursor()You can execute queries the same way:
cursor.execute("SELECT version();")
print(cursor.fetchone())Some tips:
- If you're connecting over SSL, you may need to add
sslmode='require'or similar. - Like with MySQL, always remember to commit after writes.
Bonus: ORM Option with SQLAlchemy
If you're looking for something more flexible or abstracted, SQLAlchemy is a solid choice. It supports multiple backends and lets you define models instead of writing raw SQL.
Install it:
pip install sqlalchemy
Basic usage:
from sqlalchemy import create_engine
engine = create_engine("sqlite:///example.db")
connection = engine.connect()Or for PostgreSQL:
engine = create_engine("postgresql://user:password@localhost/dbname")It takes a bit more setup but gives you cleaner code and better portability across databases.
That’s basically how you connect to different databases in Python. Each method has its own use case—SQLite for simplicity, MySQL/PostgreSQL for more serious applications, and SQLAlchemy when you want an ORM layer.
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