NameError: name 'Base' is not defined

Following is my file having all Table mapper classes.

// import statements
Class MyBase(AbstractBase, Base):
    session = None
    def __init__(self):
        global Session
        self.session = Session()
        // init statements

Class Table1(MyBase):
    // fields

engine = create_engine("...")

Session = session_maker(engine)

Base = declarative_base()

Base.meta.create_all()

1. 
   

   I am getting NameError: name 'Base' is not defined since my class is extending it before Base initialization.

   
   


2. 
   

   I can make it work, if I move engine creation, Session creation & Base creation above defining classes. But Base.meta.create_all() should be present below the class declaration. If I place Base.meta.create_all() above classes, there is no table created.

   
   


3. 
   

   I do not want to have the main() because, I am basically going to import this file in some other file.

   
   

So, I want to keep all statements(engine, session, base & create_all()) after the class definitions.