How to delete a table in SQLAlchemy?

Question

I want to delete a table using SQLAlchemy.

Since I am testing over and over again, I want to delete the table my_users so that I can start from scratch

Answer 1

Alternative to calling cls.__table__.drop(your_engine), you can try this:

Base.metadata.drop_all(bind=your_engine, tables=[User.__table__])

This method as well as the create_all() method accept an optional argument tables, which takes an iterator of sqlalchemy.sql.schema.Table instances.

You can control which tables are to be created or dropped in this way.

Answer 2

For the special case when you don't have access to the table class and just need to delete the table by table name then use this code

import logging
from sqlalchemy import MetaData
from sqlalchemy import create_engine
from sqlalchemy.engine.url import URL
from sqlalchemy.ext.declarative import declarative_base

DATABASE = {
   'drivername': 'sqlite',
   # 'host': 'localhost',
   # 'port': '5432',
   # 'username': 'YOUR_USERNAME',
   # 'password': 'YOUR_PASSWORD',
   'database': '/path/to/your_db.sqlite'
}

def drop_table(table_name):
   engine = create_engine(URL(**DATABASE))
   base = declarative_base()
   metadata = MetaData(engine, reflect=True)
   table = metadata.tables.get(table_name)
   if table is not None:
       logging.info(f'Deleting {table_name} table')
       base.metadata.drop_all(engine, [table], checkfirst=True)

drop_table('users')

Answer 3

Just call drop() against the table object. From the docs:

Issue a DROP statement for this Table, using the given Connectable for connectivity.

In your case it should be:

User.__table__.drop()

---

If you get an exception like:

sqlalchemy.exc.UnboundExecutionError: Table object 'my_users' is not bound to an Engine or Connection. Execution can not proceed without a database to execute against

You need to pass the engine:

User.__table__.drop(engine)

Answer 4

Below is example code you can execute in iPython to test the creation and deletion of a table on Postgres

from sqlalchemy import * # imports all needed modules from sqlalchemy

engine = create_engine('postgresql://python:python@127.0.0.1/production') # connection properties stored

metadata = MetaData() # stores the 'production' database's metadata

users = Table('users', metadata,
Column('user_id', Integer),
Column('first_name', String(150)),
Column('last_name', String(150)),
Column('email', String(255)),
schema='python') # defines the 'users' table structure in the 'python' schema of our connection to the 'production' db

users.create(engine) # creates the users table

users.drop(engine) # drops the users table

You can also preview my article on Wordpress with this same example and screenshots: oscarvalles.wordpress.com (search for SQL Alchemy).