迭代 python 个嵌套列表

Question

我需要将列表 'a' 转换为列表 'b' ，怎么做？

a = [[[1, 2, 3], [4, 5, 6]], [[7, 8, 9], [10, 11, 12,]]]

b = [[[1, 2, 3, 4, 5, 6]], [[7, 8, 9, 10, 11, 12,]]]

Answer 1

您可以使用列表理解：这假设您在每个子列表中只有两个子子列表。既然你的输入输出都非常清楚，那它就如你所愿

a = [[[1, 2, 3], [4, 5, 6]], [[7, 8, 9], [10, 11, 12,]]]
b = [[c[0] + c[1]] for c in a ]
print (b)

输出

[[[1, 2, 3, 4, 5, 6]], [[7, 8, 9, 10, 11, 12]]]

Answer 2

您可以使用 sum() 的巧妙技巧来加入嵌套列表：

[[sum(l, [])] for l in a]
#[[[1, 2, 3, 4, 5, 6]], [[7, 8, 9, 10, 11, 12]]]

为了更清楚地说明为什么这样做，请考虑以下示例：

>>> sum([[1,2], [3,4]], [])
[1, 2, 3, 4]

或者您可以使用更高效的 itertools.chain_from_iterable 方法：

flatten = itertools.chain.from_iterable
[[list(flatten(l))] for l in a]
#[[[1, 2, 3, 4, 5, 6]], [[7, 8, 9, 10, 11, 12]]]

Answer 3

我建议以下列表理解：

In [1]: a = [[[1, 2, 3], [4, 5, 6]], [[7, 8, 9], [10, 11, 12,]]]
   ...:

In [2]: [[[a for sub in nested for a in sub]] for nested in a]
Out[2]: [[[1, 2, 3, 4, 5, 6]], [[7, 8, 9, 10, 11, 12]]]

相当于下面的嵌套for循环：

result = []
for nested in a:
    _temp = []
    for sub in nested:
        for a in sub:
            _temp.append(a)
    result.append([_temp])

不过，我更愿意这样写：

result = []
for nested in a:
    _temp = []
    for sub in nested:
        _temp.extend(sub)
    result.append([_temp])

Answer 4

实现两个列表串联的另一种方法如下：

a = [[[1, 2, 3], [4, 5, 6]], [[7, 8, 9], [10, 11, 12,]]]

b = list(map(lambda elem: [[*elem[0], *elem[1]]],a))
print(b)

输出：

[[[1, 2, 3, 4, 5, 6]], [[7, 8, 9, 10, 11, 12]]]

Answer 5

我建议使用循环方法。

a = [[[1, 2, 3], [4, 5, 6]], [[7, 8, 9], [10, 11, 12,]]]
b = []
for i in a:
    new_j = []
    for j in i:
        new_j.extend(j)
    new_i = [new_j]
    b = b + [new_i]
b

迭代 python 个嵌套列表

iteration over python nested lists

python

nested

list

nested-lists