SQLAlchemy ORM - Creating Session


In order to interact with the database, we need to obtain its handle. A session object is the handle to database. Session class is defined using sessionmaker() – a configurable session factory method which is bound to the engine object created earlier.

from sqlalchemy.orm import sessionmaker
Session = sessionmaker(bind = engine)

The session object is then set up using its default constructor as follows −

session = Session()

Some of the frequently required methods of session class are listed below −

Sr.No. Method & Description
1

begin()

begins a transaction on this session

2

add()

places an object in the session. Its state is persisted in the database on next flush operation

3

add_all()

adds a collection of objects to the session

4

commit()

flushes all items and any transaction in progress

5

delete()

marks a transaction as deleted

6

execute()

executes a SQL expression

7

expire()

marks attributes of an instance as out of date

8

flush()

flushes all object changes to the database

9

invalidate()

closes the session using connection invalidation

10

rollback()

rolls back the current transaction in progress

11

close()

Closes current session by clearing all items and ending any transaction in progress

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