For https://stackoverflow.com/q/68940834/982257

dbwrapper.py

class DatabaseWrapper:
    def __init__(self, params=None):
        if params is None:
            # read connection params from a config file (?)
            params = self.config()
            
        self.connection_params = params
        self.connection = None
        
    def config(self):
        """Reads database config from...somewhere."""
        
    def connect(self):
        """Creates a database connection--if already connected this is a no-op."""
        
        if self.connection is not None:
            return
        
        self.connection = psycopg.connect(**self.connection_params)
        
    def disconnect(self):
        if self.connection is not None:
            self.connection.close()
            self.connection = None

    def execute_sql(self, sql_statement):
        """Execute a SQL query."""
  ` `
        self.connect()
    
        with self.connection:
            # Using the connection in a context manager guarantees clean rollback
            # on error, and commit on successful transactions
            # You don't need the 'mode' argument from your version.
            with conn.cursor() as cur:
                cur.execute(sql_statement)
                
                # If this was a SELECT this will return all the results (dangerous for
                # large queries, avoid this if possible).  Otherwise psycopg raises a
                # ProgrammingError but we can just return None
                try:
                    return cur.fetchall()
                except psycopg.ProgrammingError:
                    # Query did not return anything
                    return None