cur.execute("INSERT INTO product(store_id, url, price, charecteristics, color, dimensions) VALUES (%s, %s, %s, %s, %s, %s)", (1, 'http://www.google.com', '$20', json.dumps(thedictionary), 'red', '8.5x11'))
That will solve your problem. However, you really should be storing keys and values in their own separate columns. To retrieve the dictionary, do:
cur.execute('select charecteristics from product where store_id = 1')
dictionary = json.loads(cur.fetchone()[0])