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SQLAlchemy (sqlite3.OperationalError) no such table:

I'm using SQLAlchemy to connect to an in-memory SQLite database.
In my main.py file I have
engine = create_engine('sqlite:///:memory:', echo = True)
Base.metadata.create_all(engine)
Session = sessionmaker(bind=engine)
sess = Session()
After this I create a new thread, where I pass the session to
thread = MyThread(sess)
thread.start()
I have created my tables in tables.py like this
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String, Float
Base = declarative_base()
class My_Entry(Base):
__tablename__ = 'my_entry'
id = Column(Integer, primary_key=True)
name = Column(String)
url = Column(String)
My_Thread looks like this
class MyThread(Thread):
def __init__(sess):
Thread.__init__(self)
self.sess = sess
def run(self):
last_entry_url = self.sess.query(My_Entry).filter_by(name=key).all()[-1]
I try to query the database in the run function of my thread
last_entry_url = self.sess.query(My_Entry).filter_by(name=key).all()[-1]
but this throws an error
(sqlite3.OperationalError) no such table: my_entry
But creating the tables is one of the first things I do?
Indeed, using the echo=True gives me
CREATE TABLE my_entry (
id INTEGER NOT NULL,
name VARCHAR,
url VARCHAR,
PRIMARY KEY (id)
)
I have a sleep statement before running MyThread. My other tables work just fine, it's only this one table that doesn't.
bonus question: is there another way to get the last entry instead of all()[-1]? I assume there is but I didn't find anything

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

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.

Inserting objects and using ids in SqlAlchemy

I have a table and populating it with object list then I need to use their IDs, but I am getting an
Instance <location at 0x457f3b0> is not bound to a Session; attribute refresh operation cannot proceed
error.
I am populating a list with objects and send it to a function to insert all at once. Then I try to use IDs.
Here is my insert all function:
def insertlocations(locationlist):
session.add_all(locationlist)
session.commit()
session.close()
then I try to get IDs:
insertlocations(neighbourhoodlist)
session.flush(neighbourhoodlist)
for neighbourhood in neighbourhoodlist:
print neighbourhood.locationid
Session is global by the way. Any further info needed?
The data are inserted, as I look in the MySQL table.

Most likely your problem is that you already close() the session in your insertlocations() function.
When you then access neighbourhood.locationid, the session is closed and thatneighbourhood object isn't bound to a session any more.
For example, this should work:
from sqlalchemy import create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String
from sqlalchemy.orm import sessionmaker
engine = create_engine('sqlite:///example.db')
engine.echo = True
Base = declarative_base()
class Location(Base):
__tablename__ = 'locations'
locationid = Column(Integer, primary_key=True)
name = Column(String)
address = Column(String)
def __init__(self, name, address):
self.name = name
self.address = address
Base.metadata.create_all(engine)
Session = sessionmaker(bind=engine)
session = Session()
def insertlocations(locationlist):
session.add_all(locationlist)
session.commit()
loc1 = Location('loc1', 'Foostreet 42')
loc2 = Location('loc2', 'Barstreet 27')
neighbourhoodlist = [loc1, loc2]
insertlocations(neighbourhoodlist)
for neighbourhood in neighbourhoodlist:
print neighbourhood.locationid
session.close()
Move session.close() out of your function and do it after you're done using that session.
Ditch the session.flush(), it's not needed since you already commit the session when you add the objects.

SQLAlchemy - Trying Eager loading.. Attribute Error

I access a a postgres table using SQLAlchemy. I want a query to have eagerloading.
from sqlalchemy.orm import sessionmaker, scoped_session, eagerload
from settings import DATABASE_USER, DATABASE_PASSWORD, DATABASE_HOST, DATABASE_PORT, DATABASE_NAME
from sqlalchemy import create_engine
from sqlalchemy import Table, Column, Integer, String, Boolean, MetaData, ForeignKey
from sqlalchemy.orm import mapper
from sqlalchemy.ext.declarative import declarative_base
def create_session():
engine = create_engine('postgres://%s:%s#%s:%s/%s' % (DATABASE_USER, DATABASE_PASSWORD, DATABASE_HOST, DATABASE_PORT, DATABASE_NAME), echo=True)
Session = scoped_session(sessionmaker(bind=engine))
return Session()
Base = declarative_base()
class Zipcode(Base):
__tablename__ = 'zipcode'
zipcode = Column(String(6), primary_key = True, nullable=False)
city = Column(String(30), nullable=False)
state = Column(String(30), nullable=False)
session = create_session()
query = session.query(Zipcode).options(eagerload('zipcode')).filter(Zipcode.state.in_(['NH', 'ME']))
#query = session.query(Zipcode.zipcode).filter(Zipcode.state.in_(['NH', 'ME']))
print query.count()
This fails with
AttributeError: 'ColumnProperty' object has no attribute 'mapper'
One without eagerloading returns the records correctly.
I am new to SQLAlchemy. I am not sure what the problem is. Any pointers?

You can only eager load on a relation property. Not on the table itself. Eager loading is meant for loading objects from other tables at the same time as getting a particular object. The way you load all the objects for a query will be simply adding all().
query = session.query(Zipcode).options(eagerload('zipcode')).filter(Zipcode.state.in_(['NH', 'ME'])).all()
The query will now be a list of all objects (rows) in the table and len(query) will give you the count.