Truncating all tables in a Postgres database

I regularly need to delete all the data from my PostgreSQL database before a rebuild. How would I do this directly in SQL? At the moment I've managed to come up with a SQL statement that returns all the commands I need to execute: SELECT 'TRUNCATE TABLE ' || tablename || ';' FROM pg_tables WHERE tableowner='MYUSER'; But I can't see a way to execute them programmatically once I have them.