Although I doubt I'm forging into unknown territory, here is a nice little way I came up with to iterate around a box or square.

```
def next_coord( w, h ):
"""
get the next x,y coordinates around your box
w,h are the width and height of your box
note, the strange ranges are to prevent getting the corners twice
this loop configuration goes around clockwise from top left
for x,y in next_coord(3,3):
print "(%d,%d)" % (x,y),
>>> (0,0) (1,0) (2,0) (2,1) (2,2) (1,2) (0,2) (0,1)
"""
for x in range(0,w-1): # top
yield x,0
for y in range(0,h-1): # right
yield w-1,y
for x in range(w-1,0,-1): # bottom
yield x,h-1
for y in range(h-1,0,-1): # left
yield 0,y
```