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+"""Illustrates use of the sqlalchemy.ext.asyncio.AsyncSession object
+for asynchronous ORM use, including the optional run_sync() method.
+
+
+"""
+
+import asyncio
+
+from sqlalchemy import Column
+from sqlalchemy import ForeignKey
+from sqlalchemy import Integer
+from sqlalchemy import String
+from sqlalchemy.ext.asyncio import AsyncSession
+from sqlalchemy.ext.asyncio import create_async_engine
+from sqlalchemy.ext.declarative import declarative_base
+from sqlalchemy.future import select
+from sqlalchemy.orm import relationship
+
+Base = declarative_base()
+
+
+class A(Base):
+ __tablename__ = "a"
+
+ id = Column(Integer, primary_key=True)
+ data = Column(String)
+ bs = relationship("B")
+
+
+class B(Base):
+ __tablename__ = "b"
+ id = Column(Integer, primary_key=True)
+ a_id = Column(ForeignKey("a.id"))
+ data = Column(String)
+
+
+def run_queries(session):
+ """A function written in "synchronous" style that will be invoked
+ within the asyncio event loop.
+
+ The session object passed is a traditional orm.Session object with
+ synchronous interface.
+
+ """
+
+ stmt = select(A)
+
+ result = session.execute(stmt)
+
+ for a1 in result.scalars():
+ print(a1)
+ # lazy loads
+ for b1 in a1.bs:
+ print(b1)
+
+ result = session.execute(select(A).order_by(A.id))
+
+ a1 = result.scalars().first()
+
+ a1.data = "new data"
+
+
+async def async_main():
+ """Main program function."""
+
+ engine = create_async_engine(
+ "postgresql+asyncpg://scott:tiger@localhost/test", echo=True,
+ )
+ async with engine.begin() as conn:
+ await conn.run_sync(Base.metadata.drop_all)
+ await conn.run_sync(Base.metadata.create_all)
+
+ async with AsyncSession(engine) as session:
+ async with session.begin():
+ session.add_all(
+ [
+ A(bs=[B(), B()], data="a1"),
+ A(bs=[B()], data="a2"),
+ A(bs=[B(), B()], data="a3"),
+ ]
+ )
+
+ # we have the option to run a function written in sync style
+ # within the AsyncSession.run_sync() method. The function will
+ # be passed a synchronous-style Session object and the function
+ # can use traditional ORM patterns.
+ await session.run_sync(run_queries)
+
+ await session.commit()
+
+
+asyncio.run(async_main())