Probably a simple class question

[utdiscant]

Hi, i am quite new to python. I am trying (only for learning) to implement af simple grid-structure, which could be used as base for a simple 2d adventure game. My idea was to have a struct-like object which could hold 5x5 objects of the same type. Well, the code should reveal my idea. The problem is that when to code is executed, the output is:

The world
A simple table
A simple table

Which should be:

The world
A small house
A simple table

class Grid:
	"A grid class"
	a = [[None for i in range(5)] for j in range(5)]
	def __init__(self, des):
		self.description = des		

world = Grid("The world")

world.a[0][0] = Grid("A small house")

world.a[0][0].a[0][0] = Grid("A simple table")

print world.description
print world.a[0][0].description
print world.a[0][0].a[0][0].description

I think i might need to have a totally different approach here, and i am open to suggestions .

[utdiscant]

I think i might have solved this problem myself.

I thought an optimization would be to make the class definition like this:

class Grid:
	"A grid class"
	def __init__(self, des, width, height):
		self.description = des
		self.a = [[None for i in range(height)] for j in range(width)]

And that solved the problem. Now i just need to know why