How to create a single table using SqlAlchemy declarative_base

python sql sqlalchemy declarative
alphanumeric picture alphanumeric · Jul 23, 2017 · Viewed 10.7k times · Source

To create the User table I have to use drop_all and then create_all methods. But these two functions re-initiate an entire database. I wonder if there is a way to create the User table without erasing (or dropping) any existing tables in a database?

import sqlalchemy
from sqlalchemy.ext.declarative import declarative_base
Base = declarative_base()


class User(Base):
    __tablename__ = 'users'
    id = sqlalchemy.Column(sqlalchemy.Integer, primary_key=True)
    name = sqlalchemy.Column(sqlalchemy.String)

    def __init__(self, code=None, *args, **kwargs):
        self.name = name


url = 'postgresql+psycopg2://user:[email protected]/my_db'
engine = sqlalchemy.create_engine(url)
session = sqlalchemy.orm.scoped_session(sqlalchemy.orm.sessionmaker())
session.configure(bind=engine, autoflush=False, expire_on_commit=False)

Base.metadata.drop_all(engine)
Base.metadata.create_all(engine)

Answer

univerio picture univerio · Jul 24, 2017

You can create/drop individual tables:

User.__table__.drop(engine)
User.__table__.create(engine)

Related questions

SQLAlchemy - order_by on relationship for join table

I'm using declarative SQLAlchemy and I have three models: Role, Permission, and RolePermission. In my Role model, I have the following: class Role(Base): name = Column(u'NAME', VARCHAR(50), nullable=False, unique=True) permissionLinks = relationship(RolePermission, backref="role", order_by=name) …

Read More
How to execute raw SQL in Flask-SQLAlchemy app

How do you execute raw SQL in SQLAlchemy? I have a python web app that runs on flask and interfaces to the database through SQLAlchemy. I need a way to run the raw SQL. The query involves multiple table joins …

Read More
sqlalchemy: how to join several tables by one query?

I have the following SQLAlchemy mapped classes: class User(Base): __tablename__ = 'users' email = Column(String, primary_key=True) name = Column(String) class Document(Base): __tablename__ = "documents" name = Column(String, primary_key=True) author = Column(String, ForeignKey("users.email")) class DocumentsPermissions(…

Read More