Python: Define Object Variable Without Initialization

I am trying to rewrite my code from one big function to oop. If I have this, it crash on session.add(a1) # Unresolved reference: from sqlalchemy.ext.declarative import declarative_

Solution 1:

In Java you'd do this.session = ...; in Python that's self.session = ....

Solution 2:

The methods on your Main class look like they belong in the Address class.

engine = create_engine('mysql://test:test@localhost:3306/test', echo=False)
session = sessionmaker(bind=engine)

classAddress(Base):
    __tablename__ = 'address'id = Column(Integer, primary_key=True)
    street = Column(String, nullable=False)
    city = Column(String, nullable=False)
    # you are missing some fields you'll need eventually
    state = Column(String, nullable=False)
    zip_code = Column(String, nullable=False)  # this can be an int if you don't have to worry about Canadian zips which have letters in them
    user = relationship('User', back_populates="address")

    def__init__(self, street, city, state, zip_code, user):
        self.street = street
        self.city = city
        self.state = state
        self.zip_code = zip_code
        self.user = user

    definsert(self, session):
        #   INSERT
        session.add(self)
        session.commit()

You shouldn't create the session as part of a class because then you will be creating a new one every time you instantiate a class. Keep the session in the global space and pass it in to your methods/functions that need it as a parameter (don't use global).

Now with everything in right place you can use it like this:

from models import session, Addressaddr= Address('123 Test St.', 'Sometown', 'NY', '12345', some_user)
addr.insert(session)

Solution 3:

You are initializing local variable session in the __init__ method and calling for it in a method this variable is unknown to.

use self.varialbe in both cases instead

Solution 4:

use self.session to save variables in session