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sqlalchemy.exc.OperationalError: (sqlite3.OperationalError) no such table: items

I don't understand why I have this error. Please explain the error.
I used official documentation.
I run Pipenv virtual env:
python 3.8.2
sqlalchemy 1.3.16
You can try run this code too.
import enum
from sqlalchemy import create_engine, Column, Integer, String, Enum
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker
engine = create_engine('sqlite:///:memory:', echo=True)
Base = declarative_base()
Session = sessionmaker(bind=engine)
session = Session()
class Type(str, enum.Enum):
ONE = "one"
TWO = "two"
class Item(Base):
__tablename__ = 'items'
id = Column(Integer, primary_key=True, index=True)
name = Column(String, unique=True, index=True)
type = Column(Enum(Type), default=Type.ONE, nullable=False)
item = Item(name="item_name", type="one")
session.add(item)
print(Item.__table__)
session.commit()
for name in session.query(Item.name):
print(name)

I added:
engine = create_engine('sqlite:///:memory:', echo=True)
Base = declarative_base()
Base.metadata.create_all(bind=engine)
Session = sessionmaker(bind=engine)
session = Session()
It creates the tables in the database (there are ways of using SQLAlchemy with preexisting tables, so an explicit instruction isd necessary).

In case it ends up helping someone, my issue was due to using an in memory sqlite db to unittest an API. Pytest would set up the database and tables with one connection while the API would create its own separate connection when the test were hitting endpoints. This ultimately solved it for me.
engine = create_engine("sqlite:///:memory:", poolclass=StaticPool, connect_args={'check_same_thread': False})
Ref: https://docs.sqlalchemy.org/en/14/dialects/sqlite.html#using-a-memory-database-in-multiple-threads

pandas.read_sql Read uncommitted with SQLAlchemy

I am trying to use the pandas function pd.read_sql to read records that have been created, added, and flushed in a SQLAlchemy session, but not committed. So I want to create an object in a SQLAlchemy session and query it with pandas before calling commit. Using pandas 0.22.0 and SQLAlchemy 1.1.10.
I have tried setting the isolation_level on create_engine, and various other ways of setting the isolation level to 'READ UNCOMMITTED', but this does not seem to work. Minimal example below:
# Import packages
import pandas as pd
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import create_engine, Column, Integer, String
from sqlalchemy.orm import sessionmaker
# Set up an example ORM
Base = declarative_base()
class Record(Base):
__tablename__ = 'records'
id = Column(Integer, primary_key=True)
foo = Column(String(255))
# Create a session and engine:
database='foobar'
user=''
password = ''
host = 'localhost'
port = '5432'
connection_string = f"postgresql+psycopg2://{user}:{password}#{host}:{port}/{database}"
engine = create_engine(connection_string, encoding = 'utf8', convert_unicode = True,
isolation_level='READ_UNCOMMITTED'
)
session = sessionmaker()
session.configure(bind=engine)
db = session()
# Set up the example record:
Record.__table__.create(bind=engine)
record = Record(foo='bar')
db.add(record)
db.flush()
# Attempt to query:
records = pd.read_sql('select * from records', db.get_bind())
assert records.empty
I am looking for a solution that will cause the above code to throw an AssertionError on the last line. records.empty currently evaluates to true.

And of course I figure it out as soon as I post here. For posterity: use db.connection() instead of db.get_bind().

sqlalchemy reflected table to orm?

I reflected an existing sqlalchemy table using:
import sqlalchemy as sa
db_engine = sa.create_engine('postgres+psycopq2://postgres:pwrd#localhost/test')
meta = sa.MetaData()
records = sa.Table('records', meta, autoload=True, autoload_with=db_engine)
now when I try to add data into it via
from sqlalchemy.orm insert sessionmaker
Session = sessionmaker(bind=db_engine)
session = Session()
new_record = records(Col1='sdf', Col2='sdsfdadf')
session.add(new_record)
session.commit()
I get an error with
TypeError: 'Table' object is not callable
isn't a reflected table usable in the same way that a declared table is?

You have to declare your own model class first, as Ilja Everilä suggested:
from sqlalchemy.ext.declarative import declarative_base
Base = declarative_base()
class Records(Base):
__table__ = sa.Table('records', meta, autoload=True, autoload_with=db_engine)
Then you may use the new model class Records to operate database:
new_record = Records(Col1='sdf', Col2='sdsfdadf')
session.add(new_record)
session.commit()

SQLAlchemy: update & delete value from database

I'm newer in SQLAlchemy I use some examples to create table and insert information to it and it's working 100% .
But what I didn't find is some example for how can I update & delete some information from the database.
What I'm doing is :
from sqlalchemy import Column, ForeignKey, Integer, String
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker
from sqlalchemy import create_engine
Base = declarative_base()
## create
class Person(Base):
__tablename__ = 'person'
id = Column(Integer, primary_key=True)
name = Column(String(250), nullable=False)
engine = create_engine('sqlite:///database.db')
Base.metadata.create_all(engine)
## insert
Base.metadata.bind = engine
DBSession = sessionmaker(bind=engine)
session = DBSession()
new_person = Person(name='new person')
session.add(new_person)
session.commit()
## fetch
getperson = session.query(Person).first()
print getperson.name
# this will print : new person
# I need some example to how can I update and delete this : new person
So in this code it'll print "new person" my question is how can I update or delete it ?

Here's some example on each CRUD operation in sqlalchemy (ommiting Create, Read as you already know how to perform those):
First, necessary imports and configs for any operation:
from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker
# Category, Item, User are my tables
from database_setup import Base, Category, Item, User
# Generating session to connect to the db's ORM
engine = create_engine('sqlite:///catalogwithusers.db') # my db
Base.metadata.bind = engine
DBSession = sessionmaker(bind = engine)
session = DBSession()
Then peforming an update:
# Get the item filtering by it's id using a one() query on Item table
# If query is not empty, update the attributes, add query to session and commit
q = session.query(Item).filter_by(id=item_id).one()
if q != []:
q.name = edited_name
q.description = edited_description
session.add(q)
session.commit()
Finally, performing a deletion:
# Again get the item similarly to the example above
# Then if query returned results, use the delete method and commit
q = session.query(Item).filter_by(id=item_id).one()
if q != []:
session.delete(q)
session.commit()
These examples are taken from here. I suggest you have a look. ORM Creation is inside database_setup.py and CRUD ops are performed inside project.py and populatecatalog.py.

How to commit another object in a property of an object in sqlalchemy?

As the title says.
Here are the codes.
from sqlalchemy import Column, ForeignKey, Integer, String, DateTime, func, Boolean
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import relationship
from sqlalchemy.orm import sessionmaker
from sqlalchemy.orm import scoped_session
from sqlalchemy import create_engine
import sqlalchemy.exc
from sqlalchemy import event
from settings import DB_HOST
def return_a_scoped_session():
engine = create_engine(DB_HOST)
session_factory = sessionmaker(bind=engine)
db_session = scoped_session(session_factory)
return db_session()
Base = declarative_base()
class MyClass(Base):
"""Doc string for MyClass"""
__tablename__ = 'my_table'
file_name = Column(String(512), nullable=True)
class Aria2Jobs(Base):
__tablename__ = 'nh_downloading_jobs'
id = Column(Integer, primary_key = True)
file_name = Column(String(512), nullable=True)
is_verified = Column(Boolean, default=False, nullable=True)
def check_if_verified(self):
if self.is_verified:
# create an instance
a_job= MyClass(file_name=self.file_name)
_session = return_a_scoped_session()
_session.add(a_job)
_session.commit()
_session.close()
# event
#event.listens_for(Aria2Jobs.is_verified, 'set')
def send_to_jsonpyes_jobs(target, value, oldvalue, initiator):
target.check_if_verified()
# error is when I set a property of an object (this property will trigger an event 'set' and the event will try to commit a session.
session = return_a_scoped_session()
row = session.query(Aria2Jobs).first()
row.is_verified = True
session.add(row)
# the error came out
#
# sqlalchemy.exc.invalidrequesterror object is already attached to session
session.commit()
# How to commit another object in a property of an object?
How to commit another object in a property of an object in sqlalchemy?
As you can see, when I tried session.add(row),
error:
sqlalchemy.exc.invalidrequesterror object is already attached to session
I don't know which session the row is attached to.
I want to run the function check_if_verified
-- latest error --
sqlalchemy.exc.InvalidRequestError: Object '<Aria2Jobs at 0x7fad3a635050>' is already attached to session '1' (this is

Just remove session.add(row). Becouse you used session.query the row object is already in your session.
To save the data is enough to run session.commit function

You're using scoped_session incorrectly. What's happening here is each time you call return_a_scoped_session() it's returning a new session, with a completely new engine. row is being added to a different session somewhere else. (In fact, the code you posted doesn't even show the other places it's being added; I can't reproduce your error with the code you posted.) The solution is to fix your scoped_session:
engine = create_engine(DB_HOST)
Session = scoped_session(sessionmaker(bind=engine))
def return_a_scoped_session():
return Session()