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.

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

Answer 1

You should use

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

Otherwise you get 4 references to the same list