Question

如果我有像dims =（2,3,4）这样的维度元组，并且我想为这个数组生成所有可能索引的列表，我发现一个很好的解决方案是：

dims = (2, 3, 4)
indices = [range(0, d) for d in dims]
strings = ["[%i][%i][%i]" % (i,j,k) for i in indices[0] for j in indices[1] for k in indices[2]]
print strings:
['[0][0][0]', '[0][0][1]', '[0][0][2]', '[0][0][3]', '[0][1][0]', '[0][1][1]', '[0][1][2]', '[0][1][3]', '[0][2][0]', '[0][2][1]', '[0][2][2]', '[0][2][3]', '[1][0][0]', '[1][0][1]', '[1][0][2]', '[1][0][3]', '[1][1][0]', '[1][1][1]', '[1][1][2]', '[1][1][3]', '[1][2][0]', '[1][2][1]', '[1][2][2]', '[1][2][3]']

这一切都很好，但我正在寻找一种很好的紧凑方式来生成字符串变量，其中dims具有任意长度。我试图避免一堆“if-else”条款，具体取决于dims的长度。有什么想法吗？

Answer 1

使用product中的itertools：

In [3]: import itertools

In [4]: dims = (2, 3, 4)

In [5]: for idx in itertools.product(*map(range, dims)):
    ...:     print(idx)
    ...:
(0, 0, 0)
(0, 0, 1)
(0, 0, 2)
(0, 0, 3)
(0, 1, 0)
(0, 1, 1)
(0, 1, 2)
(0, 1, 3)
(0, 2, 0)
(0, 2, 1)
(0, 2, 2)
(0, 2, 3)
(1, 0, 0)
(1, 0, 1)
(1, 0, 2)
(1, 0, 3)
(1, 1, 0)
(1, 1, 1)
(1, 1, 2)
(1, 1, 3)
(1, 2, 0)
(1, 2, 1)
(1, 2, 2)
(1, 2, 3)

至于处理字符串，有很多方法。这是一种快速而又肮脏的方式：

In [6]: def block_me(n):
    ...:     return "[" + str(n) + "]"
    ...:

In [7]: for idx in itertools.product(*map(range, dims)):
    ...:     print("".join([block_me(i) for i in idx]))
    ...:
[0][0][0]
[0][0][1]
[0][0][2]
[0][0][3]
[0][1][0]
[0][1][1]
[0][1][2]
[0][1][3]
[0][2][0]
[0][2][1]
[0][2][2]
[0][2][3]
[1][0][0]
[1][0][1]
[1][0][2]
[1][0][3]
[1][1][0]
[1][1][1]
[1][1][2]
[1][1][3]
[1][2][0]
[1][2][1]
[1][2][2]
[1][2][3]

Answer 2

使用itertools.product：

>>> from itertools import product
>>> dims = (2, 3, 4, 5)
>>> list(product(*map(range, dims)))
[(0, 0, 0, 0), (0, 0, 0, 1), (0, 0, 0, 2), (0, 0, 0, 3), (0, 0, 0, 4), (0, 0, 1, 0), (0, 0, 1, 1), (0, 0, 1, 2), (0, 0, 1, 3), (0, 0, 1, 4), (0, 0, 2, 0), (0, 0, 2, 1), (0, 0, 2, 2), (0, 0, 2, 3), (0, 0, 2, 4), (0, 0, 3, 0), (0, 0, 3, 1), (0, 0, 3, 2), (0, 0, 3, 3), (0, 0, 3, 4), (0, 1, 0, 0), (0, 1, 0, 1), (0, 1, 0, 2), (0, 1, 0, 3), (0, 1, 0, 4), (0, 1, 1, 0), (0, 1, 1, 1), (0, 1, 1, 2), (0, 1, 1, 3), (0, 1, 1, 4), (0, 1, 2, 0), (0, 1, 2, 1), (0, 1, 2, 2), (0, 1, 2, 3), (0, 1, 2, 4), (0, 1, 3, 0), (0, 1, 3, 1), (0, 1, 3, 2), (0, 1, 3, 3), (0, 1, 3, 4), (0, 2, 0, 0), (0, 2, 0, 1), (0, 2, 0, 2), (0, 2, 0, 3), (0, 2, 0, 4), (0, 2, 1, 0), (0, 2, 1, 1), (0, 2, 1, 2), (0, 2, 1, 3), (0, 2, 1, 4), (0, 2, 2, 0), (0, 2, 2, 1), (0, 2, 2, 2), (0, 2, 2, 3), (0, 2, 2, 4), (0, 2, 3, 0), (0, 2, 3, 1), (0, 2, 3, 2), (0, 2, 3, 3), (0, 2, 3, 4), (1, 0, 0, 0), (1, 0, 0, 1), (1, 0, 0, 2), (1, 0, 0, 3), (1, 0, 0, 4), (1, 0, 1, 0), (1, 0, 1, 1), (1, 0, 1, 2), (1, 0, 1, 3), (1, 0, 1, 4), (1, 0, 2, 0), (1, 0, 2, 1), (1, 0, 2, 2), (1, 0, 2, 3), (1, 0, 2, 4), (1, 0, 3, 0), (1, 0, 3, 1), (1, 0, 3, 2), (1, 0, 3, 3), (1, 0, 3, 4), (1, 1, 0, 0), (1, 1, 0, 1), (1, 1, 0, 2), (1, 1, 0, 3), (1, 1, 0, 4), (1, 1, 1, 0), (1, 1, 1, 1), (1, 1, 1, 2), (1, 1, 1, 3), (1, 1, 1, 4), (1, 1, 2, 0), (1, 1, 2, 1), (1, 1, 2, 2), (1, 1, 2, 3), (1, 1, 2, 4), (1, 1, 3, 0), (1, 1, 3, 1), (1, 1, 3, 2), (1, 1, 3, 3), (1, 1, 3, 4), (1, 2, 0, 0), (1, 2, 0, 1), (1, 2, 0, 2), (1, 2, 0, 3), (1, 2, 0, 4), (1, 2, 1, 0), (1, 2, 1, 1), (1, 2, 1, 2), (1, 2, 1, 3), (1, 2, 1, 4), (1, 2, 2, 0), (1, 2, 2, 1), (1, 2, 2, 2), (1, 2, 2, 3), (1, 2, 2, 4), (1, 2, 3, 0), (1, 2, 3, 1), (1, 2, 3, 2), (1, 2, 3, 3), (1, 2, 3, 4)]

任意数量的变量

2 个答案: