Can you give an example of how transaction isolation is implemented in a database?

Database transaction isolation ensures that concurrent transactions do not affect each other, preventing issues such as dirty reads, non-repeatable reads, and phantom reads.

Example in Python using SQLAlchemy library and PostgreSQL:

from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker

engine = create_engine('postgresql://user:password@localhost/dbname')
Session = sessionmaker(bind=engine)
session = Session()

try:
    # Set transaction isolation level
    session.connection(
        execution_options={'isolation_level': 'SERIALIZABLE'}
    )

    # Begin transaction
    session.begin()

    # Perform database operations
    # ...

    session.commit()
except Exception as e:
    session.rollback()
    print(f'Error: {e}')
finally:
    session.close()

Here, the SERIALIZABLE isolation level guarantees maximum transaction isolation. Different DBMSs and drivers may set the isolation level differently, but the essence is that the transaction sees a consistent state of data and does not conflict with other transactions.