changing a 3D list into a 2D list

Question

I want to convert a 3D list (list_1) into a 2D list (list_2). For example:

list_1: [[[3], [4]], [[5], [6]], [[7], [8]]]
list_2: [[3, 4], [5, 6], [7, 8]]

This is what I have already tried:

[e for sl in lst for e in sl]

But the result would be different:

[[3], [4], [5], [6], [7], [8]]

Answer 1

For readibility I'd suggest itertools.chain to flatten the inner lists here:

from itertools import chain
l = [[[3], [4]], [[5], [6]], [[7], [8]]]

[list(chain.from_iterable(i)) for i in l]
# [[3, 4], [5, 6], [7, 8]]

---

Following your approach, you'd need an extra level of looping to flatten the inner lists:

[[i for e in sl for i in e] for sl in l]
# [[3, 4], [5, 6], [7, 8]]

Answer 2

另外一个选项：

[reduce(list.__add__, x)  for x in list_1]

Answer 3

you can also do it like this:

l = [[[3], [4]], [[5], [6]], [[7], [8]]]

print ([sum(item, []) for item in l])

output:

[[3, 4], [5, 6], [7, 8]]

Answer 4

您接近：

[[c for b in a for c in b] for a in lst]

Answer 5

If all your nested lists contain single elements, you can use unpacking:

d = [[[3], [4]], [[5], [6]], [[7], [8]]]
new_d = [[i for [i] in b] for b in d]

Output:

[[3, 4], [5, 6], [7, 8]]