Add Python notes

python/sqlalchemy/core.py

@@ -64,7 +64,9 @@ with engine.begin() as conn:
 # SELECT
 from sqlalchemy import select
 
-stmt = select(user_table).where(user_table.c.name == 'spongebob')
+stmt = select(user_table).where(user_table.c.name == 'spongebob')  # Where accepts binary expression
+print('Where clause: ', user_table.c.name == 'spongebob')
+print('Type of where clause: ', type(user_table.c.name == 'spongebob'))
 with engine.connect() as conn:
     for row in conn.execute(stmt):
         print(row)

python/sqlalchemy/orm.py

@@ -44,11 +44,86 @@ engine = create_engine("sqlite+pysqlite:///:memory:", future=True)
 Base.metadata.create_all(engine)
 
 
+session = Session(engine)
+
+
+# INSERT
+print('-----insert-----')
+squidward = User(name="squidward", fullname="Squidward Tentacles")
+krabs = User(name="ehkrabs", fullname="Eugene H. Krabs")
+spongebob = User(name='spongebob', fullname='Spongebob Squarepants')
+
+session.add(squidward)
+session.add(krabs)
+session.add(spongebob)
+print('new: ', session.new)
+
+saved_krabs = session.get(User, 2)
+print('krabs: ', saved_krabs)
+print('krabs is krabs: ', saved_krabs is krabs)
+session.commit()  # All changes are applied only after commit
+
+
 
 
 # SELECT
+print('-----select-----')
 from sqlalchemy import select
-stmt = select(User).where(User.name == 'spongebob')
-with Session(engine) as conn:
-    for row in conn.execute(stmt):
-        print(row)
+
+stmt = select(User)
+first = session.execute(stmt).first()
+print(firs)
+
+_all = session.execute(stmt).scalars().all()
+print(_all)
+
+
+
+# UPDATE
+print('-----update-----')
+from sqlalchemy import update
+
+# Unit of work
+squid = session.execute(select(User).filter_by(name='squidward')).scalar_one()
+print('fetched squidward: ', squid)
+squid.fullname = 'Squidward Octopus'
+print('squid modified: ', squid in session.dirty)
+print('new squid status: ', session.execute(select(User).where(User.name == 'squidward')).first())
+
+# ORM enabled
+session.execute(
+    update(User).
+    where(User.name == "squidward").
+    values(fullname="Sandy Octopus Extraordinaire")
+)
+print('Squid after bulk update: ', squid.fullname)
+
+
+
+# DELETE
+print('-----delete-----')
+from sqlalchemy import delete
+
+krabs = session.get(User, 2)
+session.delete(krabs)
+session.execute(select(User).where(User.name == "ehkrabs")).first()
+print('Krabs present: ', krabs in session)
+
+# orm-enabled
+squidward = session.get(User, 1)
+session.execute(delete(User).where(User.name == "squidward"))
+print('Squidward present: ', squidward in session)
+
+
+
+# ROLLBACK
+print('-----rollback-----')
+print(squid.__dict__)
+session.rollback()
+print(squid.__dict__)
+squid.fullname
+print(squid.__dict__)
+print('Krabs present: ', krabs in session)
+
+
+session.close()