如何按索引对列表进行分组？

Question

我有一个列表列表，我需要在其中使用用户输入对元素进行分组（请参阅代码中的 split 变量）并创建新列表。我已经尝试过，但不是分组，而是单独连接元素

split = 3 # user input 
data = [[1,2], [3,4], [5,6], [7,8], [9,10], [11,12], [13,14], [15,16], [17,18]]
z = [] ; y = []
for i,d in enumerate(data):
    z.append(d)
    if (i+1)%split==0:
        y.append(z)
        z = []
xx = (y+[z])
print(xx)
[[[1, 2], [3, 4], [5, 6]], [[7, 8], [9, 10], [11, 12]], [[13, 14], [15, 16], [17, 18]], []]
# ^____________________^    ^_______________________^  this needs to be merged

输入：

data = [[1,2], [3,4], [5,6], [7,8], [9,10], [11,12], [13,14], [15,16], [17,18]]

预期输出：

[[1, 2, 3, 4, 5, 6], [7, 8, 9, 10, 11, 12], [13, 14, 15, 16, 17, 18]]

Answer 1

使用 numpy:

data = [[1,2], [3,4], [5,6], [7,8], [9,10], [11,12], [13,14], [15,16], [17,18]]
import numpy as np
print np.array(data).reshape((split,-1)).tolist()

输出：

[[1, 2, 3, 4, 5, 6], [7, 8, 9, 10, 11, 12], [13, 14, 15, 16, 17, 18]]

Answer 2

你可以试试这个 ->

split = 3
data = [[1,2], [3,4], [5,6], [7,8], [9,10], [11,12], [13,14], [15,16], [17,18]]
z=[]
x=[]
for i,j in enumerate(data):
    if i!=0 and i%split==0: 
        z.append(x)
        x=[]
    for k in j:
        x.append(k)
z.append(x)
print z

Answer 3

这是使用列表理解的一种方法：

>>> sp = 3
>>> fragment = len(data)//sp
>>> [[t for item in data[i:i+fragment] for t in item] for i in range(0, len(data), fragment)]
[[1, 2, 3, 4, 5, 6], [7, 8, 9, 10, 11, 12], [13, 14, 15, 16, 17, 18]]

这是一个基于 intertools 的秘诀：

>>> from itertools import islice, chain
>>> 
>>> [list(chain.from_iterable(islice(data, i, i+fragment))) for i in range(0, len(data), fragment)]
[[1, 2, 3, 4, 5, 6], [7, 8, 9, 10, 11, 12], [13, 14, 15, 16, 17, 18]]

Answer 4

您可以只使用 z.extend(d) 而不是 append

Answer 5

您可以像这样在基本 Python 中执行此操作：

import itertools
flatlist = [*itertools.chain(*data)]
groupsize = int(len(flatlist) / split)

data2 = [flatlist[i:i+groupsize] for i in range(0, len(flatlist), groupsize)]
print(data2)

输出为

[[1, 2, 3, 4, 5, 6], [7, 8, 9, 10, 11, 12], [13, 14, 15, 16, 17, 18]]

如何按索引对列表进行分组？

How to group list with index wise?

python

list

itertools