Introduction¶

Grids are very neat. Horton gives them a nice Python API:

>>> from horton import grid
>>> g = grid.Grid(3, 3)
>>> g[0, 0] = 1
>>> g[2, 2] = 2
>>> grid.Grid.pprint(g)
1 0 0
0 0 0
0 0 2

The grid dimensions are inclusive but notice that the indices start at 0. Trying to access a location in the grid that isn’t there will result in a KeyError:

>>> g[100, 200]
Traceback (most recent call last):
  ...
KeyError: '(100, 100) is an invalid co-ordinate'

However there are grids for which that wouldn’t be a problem:

>>> t = grid.Torus(3, 3)
>>> t[0, 0] = 1
>>> grid.Grid.pprint(t)
1 0 0
0 0 0
0 0 0
>>> t[3, 0]
1

This is because a Torus grid wraps around at the poles:

>>> t[9, 0]
1

Grids provide the Mapping interface from the collections.abc module. You can iterate over them in all the usual ways:

>>> for coordinate, value in g.items():
...     print("X: %d, Y: %d is %d" % (coordinate[0],
...                                   coordinate[1],
...                                   value))
...
X: 0, Y: 0 is 1
X: 1, Y: 0 is 0
X: 2, Y: 0 is 0
X: 0, Y: 1 is 0
X: 1, Y: 1 is 0
X: 2, Y: 1 is 0
X: 0, Y: 2 is 0
X: 1, Y: 2 is 0
X: 2, Y: 2 is 2

>>> print(" ".join(cell for cell in g))
1 0 0 0 0 0 0 0 2

Grids also have some extra attributes that are useful when working with them:

>>> small_grid = Grid(2, 2)
>>> small_grid.coordinates
[(0, 0), (1, 0), (0, 1), (1, 1)]
>>> small_grid.dimensions
(2, 2)

You can select a region of a Grid using slice notation:

>>> grid = Grid(10, 10)
>>> small_grid = grid[0:0, 4:4]
>>> small_grid[0, 0] = 1 # Note that they do not share structure
>>> Grid.pprint(small_grid)
1 0 0 0
0 0 0 0
0 0 0 0
0 0 0 0
>>> print(grid[0, 0])
0

Assuming you’ve installed the optional dependency, pygame, you can easily start rendering your Grid objects. See Pygame Integration for more information.