Flask-SQLAlchemy check if table exists in database

Question

Flask-SQLAlchemy check if table exists in database. I see similar problems, but I try not to succeed.

Flask-SQLAlchemy check if row exists in table

I have create a table object ,like this:

<class'flask_sqlalchemy.XXX'>,

now how to check the object if exists in database.

I do many try: eg:

   for t in db.metadata.sorted_tables:
            print("tablename",t.name)

some table object is created before,but it doesnt exists in database,and now they. all print. eg:print content is

tablename： table_1
tablename： table_2
tablename： table_3

but only table_1 is exist datable，table_2 and table_3 is dynamica create，now I only want use the table_1.

very thanks.

Answer 1

I used these methods. Looking at the model like you did only tells you what SHOULD be in the database.

import sqlalchemy as sa

def database_is_empty():
    table_names = sa.inspect(engine).get_table_names()
    is_empty = table_names == []
    print('Db is empty: {}'.format(is_empty))
    return is_empty

def table_exists(name):
    ret = engine.dialect.has_table(engine, name)
    print('Table "{}" exists: {}'.format(name, ret))
    return ret

There may be a simpler method than this:

def model_exists(model_class):
    engine = db.get_engine(bind=model_class.__bind_key__)
    return model_class.metadata.tables[model_class.__tablename__].exists(engine)