使用索引的字典理解

Question

如何使用字典推导得到这段代码的等效结果？

dict_sq = dict()
i = 0
for y in range(grid_height):
    for x in range(grid_width):
        dict_sq[(x, y)] = i
        i = i + 1

{(0, 0): 0, (0, 1): 1, (0, 2): 2, (1, 0): 3, (1, 1): 4, (1, 2): 5, (2, 0): 6, (2, 1): 7, (2, 2): 8}

我使用这种方法获得了相同的结果，但键和值颠倒了：

dict(enumerate((x, y) for y in range(grid_height) for x in range(grid_width)))

但我需要索引作为值而不是键。有一种使用枚举的优雅方法吗？

Answer 1

使用字典理解一次性反转键和值：

>>> {
...     (x, y): i
...     for i, (x, y)
...     in enumerate((x, y) for x in range(grid_height) for y in range(grid_height))
... }
{(0, 0): 0, (0, 1): 1, (0, 2): 2, (1, 0): 3, (1, 1): 4, (1, 2): 5, (2, 0): 6, (2, 1): 7, (2, 2): 8}

Answer 2

这个怎么样？

from itertools import product
d = {(i, j): v for v, (i, j) in enumerate(product(range(grid_height), range(grid_height)))}

使用索引的字典理解

Dict comprehension using index

python

indexing

dictionary-comprehension