Python Database Access

SQLite, PostgreSQL, ORM patterns, and database operations.

Overview

Master database operations in Python.

SQLite

import sqlite3

# Connect to database
conn = sqlite3.connect('example.db')
cursor = conn.cursor()

# Create table
cursor.execute('''
    CREATE TABLE IF NOT EXISTS users (
        id INTEGER PRIMARY KEY AUTOINCREMENT,
        name TEXT NOT NULL,
        email TEXT UNIQUE NOT NULL
    )
''')

# Insert
cursor.execute(
    "INSERT INTO users (name, email) VALUES (?, ?)",
    ('Alice', 'alice@example.com')
)
conn.commit()

# Query
cursor.execute("SELECT * FROM users")
users = cursor.fetchall()
for user in users:
    print(user)

conn.close()

SQLAlchemy ORM

from sqlalchemy import create_engine, Column, Integer, String
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker

Base = declarative_base()

class User(Base):
    __tablename__ = 'users'
    
    id = Column(Integer, primary_key=True)
    name = Column(String(100))
    email = Column(String(100), unique=True)

# Create engine and session
engine = create_engine('sqlite:///example.db')
Base.metadata.create_all(engine)
Session = sessionmaker(bind=engine)
session = Session()

# CRUD operations
new_user = User(name='Bob', email='bob@example.com')
session.add(new_user)
session.commit()

users = session.query(User).all()
for user in users:
    print(user.name, user.email)

Practice

Build a database-backed REST API with SQLAlchemy.