How to append an object to multi-dimension list

Question

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Python list confusion

This is a quiestion about list of python. (My programming environment is SL4A with python)

I want a list below with inputted number "n".

[ ['a'] , [] , [] , [] ] # (this example is the list when n =4)    <- the list I want

So, I wrote a source-code below.

n = input()
array = [[]]*n
array[0].append('a')
print array

However, I can' get an output above, but also get a list as like...

[ ['a'], ['a'], ['a'], ['a'] ] #  <- wrong list

So, I have two questions.

Please tell me a source-code which is give me a list what I want.
Why does the source-code give me the wrong list?

Thanks for editting my question and telling me a past question I should comfirm before I post this question. — aaaaa0a, Nov 19 '12 at 12:56

score 3 · Accepted Answer · answered Nov 19 '12 at 12:37

3

You should use

array = [[] for x in range(n)]

Otherwise you get 4 references to the same list

answered Nov 19 '12 at 12:37

John La Rooy

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score 0 · Answer 2 · answered Nov 19 '12 at 12:44

0

When you do

array = [[]]*n

you will get a list with n same links. That is why when you edit one of the element you edit every element. To get rid of this just use something like this

for i in range(0, 4):
    array1.append([])
    array2+=[]

answered Nov 19 '12 at 12:44

Gavelock

77
8

score 0 · Answer 3 · edited Jun 20 '20 at 09:12

0

python 3.2:

n = input()
array = [[] for i in range(n)]
array[0].append('a')
print array

edited Jun 20 '20 at 09:12

Community

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answered Nov 19 '12 at 13:23

raton

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5
14

2

In Python 3.2 `print` is a function, so I don't think this syntax works? – Andy Hayden Nov 19 '12 at 14:33
1

This would be a better answer if you explained how the code you provided answers the question. – pppery Jun 21 '20 at 00:29

How to append an object to multi-dimension list

3 Answers3

python 3.2: