How to turn a list of strings into a list of lists (containing ints)

Question

I want to turn lst = ['123', '456', '789'] into lst = [[1,2,3], [4,5,6], [7,8,9]].

I tried:

for i in range(len(lst)):
    lst[i] = list(lst[i])

This produced lst = [['1','2','3'], ['4','5','6'], ['7','8','9']].

How can I turn those string numbers into integers?

Note: I can't use map.

The code you provided does not work. Please make sure your input is correct. — Mechanic Pig, Sep 20 '22 at 12:30
There *must* be *plenty* of duplicates among the existing [2,028,197 Python questions](https://stackoverflow.com/questions/tagged/python). — Peter Mortensen, Sep 23 '22 at 01:58

score 2 · Answer 1 · answered Sep 20 '22 at 12:45

2

List comprehension approach:

lst = ['123', '456', '789']
lst = [[int(i) for i in string_number] for string_number in lst]

answered Sep 20 '22 at 12:45

Karol Milewczyk

350
2
8

score 0 · Answer 2 · answered Sep 20 '22 at 12:31

Here is the solution:

lst = [['123'],['456'],['789']]
ans = []
temp = []

for i in lst:
    for j in i:
        temp = list(j)
        for k in range(len(temp)):
            temp[k] = int(temp[k])
        ans.append(temp)
        
print(ans)

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

score 0 · Answer 3 · edited Sep 23 '22 at 02:25

0

Well, here is a simple solution for your problem:

final_list = []
for i in lst:
    tmp_list = []
    text = str(i[0])
    for c in text:
        tmp_list.append(int(c))
    final_list.append(tmp_list)

edited Sep 23 '22 at 02:25

Peter Mortensen

30,738
21
105
131

answered Sep 20 '22 at 12:31

youssef

11
1

score 0 · Accepted Answer · answered Sep 20 '22 at 12:38

0

lst = ['123','456','789']
for i in range(len(lst)):
    lst[i] = [int(x) for x in lst[i]]

answered Sep 20 '22 at 12:38

Byron

192
4

How to turn a list of strings into a list of lists (containing ints)

4 Answers4