How do I create SQLAlchemy models in Python?

How do I create SQLAlchemy models in Python?

To create SQLAlchemy models, you need to define a class for each table, inheriting from Base. Here's a simple example:

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

Base = declarative_base()

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

engine = create_engine('sqlite:///:memory:')
Base.metadata.create_all(engine)

What are the key components of a SQLAlchemy model?

The key components of a SQLAlchemy model include the class definition, table name, columns, and data types. Each model class represents a table, and each class attribute corresponds to a column in that table.

Can I add relationships between models?

Yes, you can add relationships using the relationship() function. For example, if you have a Post model related to the User model, you can define it like this:

class Post(Base):
    __tablename__ = 'posts'
    id = Column(Integer, primary_key=True)
    user_id = Column(Integer, ForeignKey('users.id'))
    user = relationship('User')

How do I query data from these models?

You can query data using the session object. For example:

from sqlalchemy.orm import sessionmaker

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

users = session.query(User).filter_by(age=30).all()