python append to nested list , index out of range

Question

I am trying to create a nested list. The result would be something like [[0,1],[2,3],[0,4]] I tried the following and got an index out of range error:

list = []
list[0].append(0)

Is it not appending 0 to the first item in the list? How should I do this? Many thanks for your help.

*"Is it not appending 0 to the first item in the list?"* What first item in the list? That list is empty. — Aran-Fey, Apr 03 '19 at 09:51
I must notice that shadowing built-in name `list` with `list = []` is not a good idea. — sanyassh, Apr 03 '19 at 11:18

U12-Forward · Accepted Answer · 2019-04-03T10:10:39.540

3

A little typo, you should do:

list = [[]]
list[0].append(0)

You need to have a first element first...

Edit:

Use:

list = []
for i in range(3):
    list.append([])
    list[-1].append(0)

edited Apr 03 '19 at 10:10

answered Apr 03 '19 at 09:52

U12-Forward

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Thanks. But if it is in a loop, how do I initialise the n item before append? – user4046073 Apr 03 '19 at 10:08
@user4046073 Edited mine, – U12-Forward Apr 03 '19 at 10:10

score 1 · Answer 2 · answered Apr 03 '19 at 09:54

1

For that you'll need to append a list to a list first, i.e.:

list = []
list.append([])
list[0].append(0)
print(list)
# [[0]]

answered Apr 03 '19 at 09:54

Pedro Lobito

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score 0 · Answer 3 · edited Apr 03 '19 at 11:16

0

lst = []
lst.append([0,1])
lst.append([2,3])
lst.append([0,4])
print(lst)

How about this ? Or you need in the form of loop with constant set of numbers?

edited Apr 03 '19 at 11:16

sanyassh

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answered Apr 03 '19 at 10:53

Nasrath D

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python append to nested list , index out of range

3 Answers3