How can I make a list of lists from user input?

Question

Here is what I did-

grid_len = input("Enter Grid Length: ") #Assuming grid_length to be 3
s = []
while True:
    s.append(input())
    if len(s) == int(grid_len)**2: #grid_length^2 will be 9
        print(s)
        break

When Input is for example 1 in the first loop, 2 in the second, 3 in the third and so on upto 9; It creates a list like this:

['1','2','3','4','5','6','7','8','9']

But I want it something like this:

[[1,2,3],[4,5,6],[7,8,9]]

You want every 3 inputs by the user to create a list? And then for each of these lists to be embedded in another list? — Inbar Rose, Mar 13 '13 at 08:58
Btw, comments in python start with the hash symbol (`#`) and not `//` :p — TerryA, Mar 13 '13 at 09:00

score 5 · Answer 1 · answered Mar 13 '13 at 09:07

5

A version based on list comprehension.

s = [[input("Enter number: ") for _ in range(grid_len)] for _ in range(grid_len)]
print s

Note: Two forward slashes "//" are not valid python comment identifiers

answered Mar 13 '13 at 09:07

Ifthikhan

1,484
10
14

score 2 · Answer 2 · edited May 23 '17 at 12:31

Something I found from this question: How do you split a list into evenly sized chunks?

>>> mylist = [1,2,3,4,5,6,7,8,9]
>>> def chunks(l, n):
...    return [l[i:i+n] for i in range(0, len(l), n)]
>>> chunks(mylist,3)
[[1, 2, 3], [4, 5, 6], [7, 8, 9]]

Integrated into your code:

def chunks(l, n):
    return [l[i:i+n] for i in range(0, len(l), n)]
grid_len = input("Enter Grid Length: ")
s = []
while True:
    s.append(int(input())) # Notice I put int() around input()
    if len(s) == int(grid_len)**2:
        s = chunks(s,grid_len)
        print(s)
        break

EDIT: Changed the second parameter in chunks to match grid_len. This will now work for not just 3.

score 1 · Answer 3 · answered Mar 13 '13 at 12:57

Here's my code:

grid_len = input("Enter Grid Length: ")
s = []
for i in range(grid_len):         #looping to append rows
    s.append([])                  #append a new row
    for j in range(grid_len):     #looping to append cells
        s[-1].append(input())     #append a new cell to the last row, or you can also append to `i`th row

score 1 · Answer 4 · edited Jul 10 '19 at 05:25

1

I have got your problem, the very simple solution is

grid_length = int(input())
s = []
for i in range(grid_length):
     b = list(map(int, input().split()))
     s.append(b)
print(s)

edited Jul 10 '19 at 05:25

answered Dec 15 '18 at 12:07

coderina

1,583
13
22

score 1 · Answer 5 · edited Jan 02 '19 at 06:48

1

Try this:

arr = [list(map(int, input().split())) for i in range(int(input()))]

edited Jan 02 '19 at 06:48

CodeIt

3,492
3
26
37

answered Jan 01 '19 at 15:07

Amir

111
6

Bakuriu · Answer 6 · 2013-03-13T12:49:00.120

0

You should create a new sub-list every grid_length elements:

grid_len = int(input("Enter Grid Length: "))
s = []
for _ in range(grid_length):
    sub_list = []
    for _ in range(grid_length):
        sub_list.append(input())
    s.append(sub_list)
print(s)

Note that, in general, you should use for every time that you have to iterate sequentially over an object or you know how many times to repeat a loop. while is generally better to handle "strange" conditions that are hard to factor in terms of number of iterations or iterating over an iterable.

edited Mar 13 '13 at 12:49

answered Mar 13 '13 at 08:59

Bakuriu

98,325
22
197
231

It gives me this error in this line: for _ in range(grid_len): TypeError: 'str' object cannot be interpreted as an integer – Mar 13 '13 at 09:36
@yesboy Sorry, I'm too used to python2. I updated the code to convert the size to an integer. – Bakuriu Mar 13 '13 at 12:49
@Bakuriu `NameError: name 'grid_length' is not defined`. You will have to edit your code – S Andrew May 31 '18 at 08:41

score 0 · Answer 7 · answered Mar 13 '13 at 09:08

Using nested list comprehensions:

>>> grid_len = input("Enter Grid Length: ")
Enter Grid Length: 4
>>> incrementer = iter(xrange(1, grid_len ** 2 + 1))
>>> s = [[next(incrementer) for x in xrange(grid_len)] for y in xrange(grid_len)]
>>> print s
[[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12], [13, 14, 15, 16]]

score 0 · Answer 8 · answered Mar 13 '13 at 10:04

0

Try this:

x = [[int(input()) for c in range(grid_len)] for r in range(grid_len)]

answered Mar 13 '13 at 10:04

pradyunsg

18,287
11
43
96

score 0 · Answer 9 · answered Jul 16 '21 at 15:55

0

Try this:

grid_len = int(input()) #just one input
grid = [[input(),input(),input()] for _ in range(grid_len)] #grid_len * 3 inputs
print(grid)

answered Jul 16 '21 at 15:55

SidJ25

47
6

Try to provide a generic answer along with some added information which has not been provided in the previous answers. – Amit Gupta Jul 16 '21 at 18:38
Will do, Thanks! – SidJ25 Jul 18 '21 at 01:00

chinmayee bharati dalai · Answer 10 · 2022-07-20T16:10:18.080

Here is my code. Using this we can have different sizes of lists inside the list:

len_of_list = int(input('Enter the first layer list size: '))
list_of_list = []


for i in range(len_of_list):
  len_of_elem_inside_list = int(input('Enter the second layer list sizes: '))
  inside_list =[]

  for j in range(len_of_elem_inside_list):
    elements_in_the_list = int(input('Enter the elements inside the list of list: '))
    inside_list.append(elements_in_the_list)

  list_of_list.append(inside_list)
print('Output: ',list_of_list)

How can I make a list of lists from user input?

10 Answers10

Linked

Related