Column default value persisted to the table

I am currently using a Column that has the following signature:

Column('my_column', DateTime, default=datetime.datetime.utcnow)

I am trying to figure out how to change that in order to be able to do vanilla sql inserts (INSERT INTO ...) rather than through sqlalchemy. Basically I want to know how to persist the default on the table without lossing this functionality of setting the column to the current utc time.

The database I am using is PostgreSQL.