flask 批量导入数据的时候出现错误? 求指教!

批量添加数据报错：RuntimeError: application not registered on db instance and no application bound to current context

from app import create_app,db
from flask_script import Manager, Shell
from flask_migrate import Migrate, MigrateCommand
from script.hosts import hostinfo
from app.models import Hosts


app = create_app('default')
manager = Manager(app)
migrate = Migrate(app, db)



def make_shell_context():
return dict(app=app, db=db, Hosts=Hosts,)

manager.add_command("shell", Shell(make_context=make_shell_context))
manager.add_command('db', MigrateCommand)


hostinfo = hostinfo()
for i in hostinfo.get_host():
for info in i:
info = Hosts(netip=info['PublicIpAddress']['IpAddress'][0],
name=info['InstanceName'],
area=info['RegionId'],
osname=info['OSName'],
host_config='CPU:%s Mem:%s intout:%s' % (info['Cpu'],info['Memory'],info['InternetMaxBandwidthOut']))
db.session.add(info)
db.session.commit()


if __name__ == '__main__':
manager.run()