How to append two-dimensional python list without for loop?

Question

Let's suppose that I have 3 python two-dimensional lists (data_1, data_2, data_3) of 10x5 dimensions. I want to make one list (all_data) from them with 30x5 dimensions. For now, I am doing this by applying the following:

data_1 = [[1, 2, 3, 4, 5], [6, 7, 8, 9, 10], ..., [46, 47, 48, 49, 50]]
data_2 = [[101, 102, 103, 104, 105], [106, 107, 108, 109, 110], ..., [146, 147, 148, 149, 150]]
data_3 = [[201, 202, 203, 204, 205], [206, 207, 208, 209, 210], ..., [246, 247, 248, 249, 250]]
all_data = []
for index, item in enumerate(data_1):
    all_data.append(item)

for index, item in enumerate(data_2):
    all_data.append(item)

for index, item in enumerate(data_3):
    all_data.append(item)

If I simply do something like this:

all_data.append(data_1)
all_data.append(data_2)
all_data.append(data_3)

then I get a list of 3x10x5 which is not what I want.

So can I create a 30x5 list by appending three 10x5 lists without using any for loop?

Possible duplicate of [join list of lists in python](https://stackoverflow.com/questions/716477/join-list-of-lists-in-python) — Vivek Kalyanarangan, Feb 26 '18 at 12:39

jsmolka · Accepted Answer · 2018-02-26T13:07:31.103

7

You can just extend your list.

data = []
data.extend(d1)
data.extend(d2)
data.extend(d3)

edited Feb 26 '18 at 13:07

answered Feb 26 '18 at 12:34

jsmolka

780
6
15

Thank you for your response but this produces a 10x15 list and not a 30x5 list from the initial lists... – Outcast Feb 26 '18 at 12:43
1

No, it does not (like every answer you commented on). Consider sharing your list. – jsmolka Feb 26 '18 at 12:48

Nikolay Lebedev · Answer 2 · 2018-02-26T13:14:48.397

5

Simply write:

all_data = data_1 + data_2 + data_3

If you want to merge all the corresponding sublists of these lists, you can write:

# function that merges all sublists in single list
def flatten(l):
    return [el for subl in l for el in subl]

# zipped - is a list of tuples of corresponding items (our deep sublists) of all the lists
zipped = zip(data_1, data_3, data_3)

# merge tuples to get single list of rearranges sublists
all_data = flatten(zipped)

edited Feb 26 '18 at 13:14

answered Feb 26 '18 at 12:33

Nikolay Lebedev

346
1
9

Thank you for your response but this produces a 10x15 list and not a 30x5 list from the initial lists... – Outcast Feb 26 '18 at 12:40
1

if `data_1` and `data_2` and `data_3` contains sublists, what dimension have `data_1`? And what dimension have it's sublist? – Nikolay Lebedev Feb 26 '18 at 12:51
Thank you for completing the question. I added an alternative option to my answer. But I think that you are somewhere wrong about the dimensions of the desired list. The first option should give a dimension of 30 * 5. – Nikolay Lebedev Feb 26 '18 at 13:20
Thank you for your correct response again (two upvotes). – Outcast Feb 26 '18 at 13:28

score 1 · Answer 3 · answered Feb 26 '18 at 12:34

1

How about:

all_data = data_1 + data_2 + data_3

answered Feb 26 '18 at 12:34

man0v

654
3
13

Thank you for your response but this produces a 10x15 list and not a 30x5 list from the initial lists... – Outcast Feb 26 '18 at 12:40
1

@Universalis can you provide me with an example, please? Cuz what I've posted does what you've described up there - namely put the elements of the 3 lists(be they lists or not) into one list. How does a "10x5" list look like? – man0v Feb 26 '18 at 12:45
I think he doesn't even know how his lists look like. – jsmolka Feb 26 '18 at 12:51
@jsmolka it's very simple to run his code across any of the answers and compare the output... anyway. – man0v Feb 26 '18 at 12:52
1

Those are just one dimensional list, there is nothing two dimensional about them. – jsmolka Feb 26 '18 at 13:02
@Universalis How are those 10x5? – man0v Feb 26 '18 at 13:04
Check again please – Outcast Feb 26 '18 at 13:06
@Universalis Every code on this page returns your 30x5 list for those lists. – jsmolka Feb 26 '18 at 13:12
@Universalis how did you get 10x15 lists? Did you run that very code? Give it a try in the python command line and see for yourself. – man0v Feb 26 '18 at 13:13

score 0 · Answer 4 · answered Feb 26 '18 at 12:32

0

This should work:

data=[]
data[len(data):] = data1
data[len(data):] = data2
data[len(data):] = data3

answered Feb 26 '18 at 12:32

FlyingTeller

17,638
3
38
53

score 0 · Answer 5 · answered Feb 26 '18 at 12:37

0

In case you don't mind it being lazy, you could also do

import itertools

all_data = itertools.chain(data1, data2, data3)

answered Feb 26 '18 at 12:37

zsquare

9,916
6
53
87

How to append two-dimensional python list without for loop?

5 Answers5