將元素從列表中移出到新列表中

Question

我有一個列表，其中包含幾個子列表，每個子列表中都有一個給定數量的元素。我需要將所有子列表中的所有元素移動到另一個列表中，即：消除子列表中元素間的分離。

這是什麼，如果我的意思是MWE：

a = [[[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12], [13, 14, 15, 16]], [[17, 18, 19, 20], [21, 22, 23, 24]], [[25, 26, 27, 28], [26, 30, 31, 32], [33, 34, 35, 36]]] 

b = [] 
    for elem in a: 
     for item in elem: 
      b.append(item) 

導致：

[[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12], [13, 14, 15, 16], [17, 18, 19, 20], [21, 22, 23, 24], [25, 26, 27, 28], [26, 30, 31, 32], [33, 34, 35, 36]] 

我敢肯定有一個更優雅，更簡單的方式在Python做到這一點。

Answer 1

使用itertools.chain.from_iterable：

>>> from itertools import chain 
>>> list(chain.from_iterable(a)) 
[[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12], [13, 14, 15, 16], [17, 18, 19, 20], [21, 22, 23, 24], [25, 26, 27, 28], [26, 30, 31, 32], [33, 34, 35, 36]] 

Timing comparison:

Answer 2

試試這個：

[item for sublist in a for item in sublist]