[Tutor] list question

[Wayne]

On Tue, Aug 11, 2009 at 7:17 AM, <proportional at msn.com> wrote:

>  hi i am currently doing the 'livewires' python tutorial lesson 5. i am
> making a little game that makes a few squares chase a circle around a little
> grid. i can get the 1 square acting on 1 variable to come up, but the
> tutorial now wants me to create a list of variables that act under the same
> class.
>
> this is what i have to make the 1 square appear (which works)(i have also
> cut a lot of the program out to make this email smaller.)
>
> class Robot:
>     pass
>
> def place_robot():
>     global robot
>     robot = Robot()
>     robot.x=random_between(0,63)
>     robot.y=random_between(0,47)
>     draw_robot()
>     print robot.x
>
> and i cant figure out what to write to make the variable 'robot' work as a
> list, and then follow all the instructions 3 times. this is what i tried to
> put in.
>
> class Robot:
>     pass
>
> def place_robot():
>     global robot
>     r1 = Robot()
>     r2 = Robot()
>     r3 = Robot()
>     robot = [r1,r2,r3]
>     robot.x=random_between(0,63)
>     robot.y=random_between(0,47)
>     draw_robot()
>     print robot.x
>
> i was under the assumption that the instruction
> robot.x=random_between(0,63) would return a value 3 times for r1 r2 and r3,
> but instead i get AttributeError: 'list' object has no attribute 'x'. so i
> got no idea heh. i hope this makes sense, as im really new to programming.
>

I think what you want is:

for r in robot:
    r.x = random_between(0,63)
    r.y = random_between(0,47)
    draw_robot()
    print r.x

Now for the why:
robot is a list of objects - you declared it such with robot = [r1, r2, r3]
(incidentally you could just do robots = [Robot(), Robot(), Robot()] ), and
lists don't have x y attributes, which you're trying to access. I presume
you're really trying to access the x y attributes of your Robot() class,
which is an entirely different object from your list.

HTH,
Wayne
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