多维list初始化的方便写法

python中多维list初始化时如果这样写
d = [[None]*2]*3时是浅层拷贝，修改内容时会有牵连。。
这样写安全
d = [[None for x in xrange(2)] for x in xrange(3)]
但是又很麻烦。
在初始化一个list时，比如一个5维的，如果我想避免浅层拷贝，什么样的写法最好呢？

list

初始化

xrange

5 条回复 • 1970-01-01 08:00:00 +08:00

hhrmatata

2013-06-01 09:02:08 +08:00

以下来自Python Cookbook:

更简便的写法是：
d = [[None] * 2 for x in range(3)]
但是遵照Python的哲学，更推荐更规范和更具有可读性的写法：
d = [[None for x in xrange(2)] for x in xrange(3)]

charnugagoo

2013-06-01 10:21:31 +08:00

@hhrmatata
我现在需要初始化一个五维list ToT，这两种写法都很丑陋啊。。

sillyousu

2013-06-01 10:40:38 +08:00

def gen_list(dem, rang):
----if dem == 1:
--------return [None for x in range(rang)]
----else:
--------return [gen_list(dem-1, rang) for x in range(rang)]
这样？

五维，感觉不管怎么搞都是不好搞。想到了 list[0][1][2][3][4] 和很多层的循环嵌套。

hhrmatata

2013-06-01 11:17:49 +08:00

构造递归函数，得到任何维度的初始化：

def make(dims, n, init_value):
if n == 1:
return [init_value for i in range(dims[n - 1])]
else:
return [make(dims, n - 1, init_value) for i in range(dims[n - 1])]

>>> dims1 = [2, 3]
>>> print make(dims1, 2, None)
[[None, None], [None, None], [None, None]]

>>> dims2 = [1, 2, 3, 4, 5]
>>> print make(dims2, 5, 0)
[[[[[0], [0]], [[0], [0]], [[0], [0]]], [[[0], [0]], [[0], [0]], [[0], [0]]], [[[0], [0]], [[0], [0]], [[0], [0]]], [[[0], [0]], [[0], [0]], [[0], [0]]]], [[[[0], [0]], [[0], [0]], [[0], [0]]], [[[0], [0]], [[0], [0]], [[0], [0]]], [[[0], [0]], [[0], [0]], [[0], [0]]], [[[0], [0]], [[0], [0]], [[0], [0]]]], [[[[0], [0]], [[0], [0]], [[0], [0]]], [[[0], [0]], [[0], [0]], [[0], [0]]], [[[0], [0]], [[0], [0]], [[0], [0]]], [[[0], [0]], [[0], [0]], [[0], [0]]]], [[[[0], [0]], [[0], [0]], [[0], [0]]], [[[0], [0]], [[0], [0]], [[0], [0]]], [[[0], [0]], [[0], [0]], [[0], [0]]], [[[0], [0]], [[0], [0]], [[0], [0]]]], [[[[0], [0]], [[0], [0]], [[0], [0]]], [[[0], [0]], [[0], [0]], [[0], [0]]], [[[0], [0]], [[0], [0]], [[0], [0]]], [[[0], [0]], [[0], [0]], [[0], [0]]]]]

hhrmatata

2013-06-01 11:20:16 +08:00

好吧，代码不能缩进;回复后又不能修改