Peewee ORM Example Explanation

This document explains the Peewee ORM example provided in peewee_example.py.

Overview

The example shows how to:

1. Set up a SQLite database using Peewee
2. Define a model
3. Connect to the database
4. Perform basic CRUD operations (Create and Read)

Code Explanation

Imports and Database Setup

import os
from peewee import Model, SqliteDatabase, CharField

db_file = "peewee_example.db"
if os.path.exists(db_file):
    os.remove(db_file)

db = SqliteDatabase(db_file)

This section imports necessary modules and sets up the SQLite database file. If the file already exists, it's removed to start fresh. We then create a SqliteDatabase instance.

Model Definition

class User(Model):
    username = CharField(unique=True)
    email = CharField(unique=True)

    class Meta:
        database = db

    def __str__(self):
        return f"User: {self.username}, Email: {self.email}"

Here, we define the User model. It has two fields: username and email. The Meta class specifies which database to use. The __str__ method provides a string representation of the object.

Database Operations

def run_example():
    db.connect()
    db.create_tables([User])

    try:
        new_user = User.create(username='alice', email='alice@example.com')
        user = User.get(User.username == 'alice')
        print(user)
    except Exception as e:
        print(f"An error occurred: {e}")
    finally:
        db.close()

This function demonstrates:

1. Connecting to the database
2. Creating the necessary tables
3. Creating a new user (Create operation)
4. Retrieving that user from the database (Read operation)
5. Error handling
6. Closing the database connection

Running the Example

if __name__ == "__main__":
    run_example()
    print(f"SQLite database created at: {os.path.abspath(db_file)}")

This section runs the example when the script is executed directly and prints the location of the created database file.

Running the Example

To run this example:

1. Ensure you have Peewee installed:

   pip install peewee
   

2. Run the script:

   python peewee_example.py
   

The script will create a SQLite database file, add a user to it, retrieve and print the user's information, and then display the location of the created database file.