Create 2d list from 1d list with given length and width?

Question

How to create 2D list from 1D list with given row and cols?

Given:

sample_list=[5, 2, 3, 4, 1, 6, 1, 6, 7, 2, 3]

row=2
cols=4

It should return this:

[[5, 2, 3, 4],[1, 6, 1, 6]]

I don't need other numbers = 7, 2, 3. I just want a list that has row and cols which user gives. My solution does not return what i want,

My solution:

def 1D_to_2D(sample_list, row, cols):
    return [sample_list[i:i+cols] for i in range(0, len(sample_list), rows)]

returns:

[[5, 2, 3, 4], [3, 4, 1, 6], [1, 6, 1, 6], [1, 6, 7, 2], [7, 2, 3], [3]]

Anyone can help?

score 1 · Accepted Answer · answered Aug 02 '17 at 18:46

1

Just slice your list using a list comprehension with range and a step of cols (not rows as you used), and limit the number of items using external slicing with rows:

sample_list=[5, 2, 3, 4, 1, 6, 1, 6, 7, 2, 3]
rows=2
cols=4

result = [sample_list[x:x+cols] for x in range(0,len(sample_list),cols)][:rows]

result:

[[5, 2, 3, 4], [1, 6, 1, 6]]

answered Aug 02 '17 at 18:46

Jean-François Fabre

137,073
23
153
219

yes. but the accepted answer doesn't truncate the list, it just stops at the right moment, so it's slightly better (well, could have done with some more explanation, code is not all!) – Jean-François Fabre Aug 02 '17 at 19:08
note that I wasn't saying that to get answer acceptance from you. – Jean-François Fabre Aug 02 '17 at 19:13
(note that we're the 2 ones upvoting the other answer :)) – Jean-François Fabre Aug 02 '17 at 19:17

score 1 · Answer 2 · answered Aug 02 '17 at 18:48

1

def D_to_2D(sample_list, rows, cols):
    return [sample_list[cols*i: cols*(i+1)] for i in range(rows)]

>>> D_to_2D([5, 2, 3, 4, 1, 6, 1, 6, 7, 2, 3], 2, 4)
[[5, 2, 3, 4], [1, 6, 1, 6]]

answered Aug 02 '17 at 18:48

Huang

599
2
6

score 0 · Answer 3 · answered Aug 02 '17 at 20:20

0

f = lambda x, row, cols: [x[i:i+cols] for i in range(0, cols*row, cols)]
f(x, row, cols)

answered Aug 02 '17 at 20:20

Reza

141
1
12

What does this return? I think some context for your answer would be in place here – KenHBS Sep 28 '17 at 10:25
It returns the intended answer – Reza Sep 28 '17 at 13:51

Create 2d list from 1d list with given length and width?

3 Answers3