CODEWITHSUNDEEP
python-3.xmultidimensional-array
Anh Nhat Tran
Anh Nhat Tran

Reputation: 562

Initializing and updating a multidemensional array python3

I need to initialize a multidimensional array from an integer n.

n = 2

list_1 = [[] for _ in range(n)]
list_2 = [[]] * n

Then I append 2 to the first item in the nD-array as below.

list_1[0].append(2)
list_2[0].append(2)

print('After')
print(list_1) # [[2], []]
print(list_2) # [[2], [2]] Why this happen?

You could find the code here.

I'm new to python. Could anyone explain in-depth why when I use [[]] *n, it will update all child arrays in list_2?

Upvotes: 0

Views: 66

Answers (1)

Viet
Viet

Reputation: 12807

You can find a comprehensive answer here: Python list confusion

Basically when the array is initialized with *n, it will copy the address of the first element to all the rest.

Upvotes: 1

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