Building SQLAlchemy Objects

In this chapter, you'll learn how to set up your database session and add data to the database using SQLAlchemy. By the end, you'll understand how to create a session, add a new record, and save it. After creating the model, you can proceed to creating objects and saving them to the database.

1. Set Up the Session

A session is your primary tool for interacting with the database. Use sessionmaker to bind the engine and create a session:


python
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Session = sessionmaker(bind=engine)
session = Session()

The Session() function creates an active session that serves as a workspace for staging and preparing database operations before they are committed.

2. Add a New Object

To add data, follow these steps:

Create an Object
Instantiate a model class (e.g., Product) with the required attributes.


python
new_product = Product(name="Laptop", description="High-end gaming laptop", price=1500)

Stage the Object
Add the object to the session with add().
```
python
session.add(new_product)
```
Save the Changes
Commit the session to finalize the transaction.
```
python
session.commit()
```

Taak

Swipe to start coding

Initialize the database session using Session.
Create a new object of the Product class with the specified attributes.
Add the new object to the session using the appropriate method.
Commit the transaction to save changes to the database.

Oplossing

from sqlalchemy import create_engine, Column, Integer, String, Boolean

from sqlalchemy.orm import declarative_base, sessionmaker

# Initialize the database

engine = create_engine("sqlite:///data.db")

Base = declarative_base()

# Define the Product model

class Product(Base):

__tablename__ = "products"

id = Column(Integer, primary_key=True)

name = Column(String, nullable=False)

description = Column(String)

price = Column(Integer, nullable=False)

is_in_stock = Column(Boolean, default=True)

# Create tables

Base.metadata.create_all(engine)

# Set up the session

Session = sessionmaker(bind=engine)

session = Session()

# Add a new product

new_product = Product(name="Laptop", description="High-end gaming laptop", price=1500)

session.add(new_product)

session.commit()

print(f"Added product: {new_product}")

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Sectie 4. Hoofdstuk 5