When you iterate through your collection of Aliens, I will be an alien. So treat it like one. Instead of aliens[i].move() You would use: i.move() if i.getxpos() == x: HTH. -Rodney Please consider the environment before printing this email. From: programmingblind-bounce@xxxxxxxxxxxxx [mailto:programmingblind-bounce@xxxxxxxxxxxxx] On Behalf Of BlueScale Sent: Friday, April 17, 2009 7:17 AM To: programmingblind@xxxxxxxxxxxxx Subject: Python (Trouble with Aliens!) Hi, I am having some trouble with my aliens. Here's the code: for i in aliens: aliens[i].move() if aliens[i].getxpos() == x: lockOn.play() The error I am getting is: TypeError: object cannot be interpreted as an index Can someone please help me make my aliens behave better? Thanks