Confusing psycopg2 behavior

gistfile1.txt

(python)[kb1pkl@Ulysses:hacking/python]$ python                                   (05-27 03:21)
Python 2.7.3 (default, Apr 30 2012, 21:18:11) 
[GCC 4.7.0 20120416 (Red Hat 4.7.0-2)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import psycopg2 as pg
>>> conn = pg.connect('user=flyl dbname=flyl')
>>> c = conn.cursor()
>>> c.execute('INSERT INTO files (name, owner) VALUES (%s, %s) RETURNING id;', ("foo", "bar"))
>>> c.fetchall()
[(15,)]
>>> 
(python)[kb1pkl@Ulysses:hacking/python]$ psql -U flyl -c "SELECT * FROM files;"   (05-27 03:22)
 id | name | owner 
----+------+-------
(0 rows)

(python)[kb1pkl@Ulysses:hacking/python]$ psql -U flyl -c "INSERT INTO files (name, owner) VALUES ('foo', 'bar') RETURNING id;"
 id 
----
 16
(1 row)

INSERT 0 1
(python)[kb1pkl@Ulysses:hacking/python]$ psql -U flyl -c "SELECT * FROM files;"   (05-27 03:23)
 id | name | owner                                                             
----+------+-------
 16 | foo  | bar
(1 row)

I'm an idiot, forgot that I needed to commit.