如何从大二维列表中获取子二维列表？

Question

你怎么从一个更大的二维列表中获取一个二维子列表呢？

gridx = 10
gridy = 16

grid = [[0]*gridx for i in range(gridy)]
subgrid = None
# I want to get a subgrid given an x,y grid origin (bottom-left) and x,y subgrid size

Answer 1

我猜你把你的网格存储在一个列表的列表里，对吧？也就是说：

primary list: [ * * * * * * ]
second item:    * * * * * * 

如果是这样的话，你的解决办法就是从起点出发，沿着这些列表走到终点。

sublist = []
for x in range(startx, endx):
     sublist.append(oldlist[x][starty:endy])

Answer 2

如果你想在二维列表的边界 x1, y1, x2, y2 进行切片，你可以这样做：

def getsubgrid(x1, y1, x2, y2, grid):
    return [item[x1:x2] for item in grid[y1:y2]]

比如说：

grid = [[1, 2, 3, 4, 5, 6, 7, 8, 9],
        [11,12,13,14,15,16,17,18,19],
        [21,22,23,24,25,26,27,28,29],
        [31,32,33,34,35,36,37,38,39],
        [41,42,43,44,45,46,47,48,49],
        [51,52,53,54,55,56,57,58,59]]

print getsubgrid(3,2,5,4,grid)

#prints [[24, 25], [34, 35]]