Array-declaration issue in Python

Question

I have trouble declaring a two-dimensional list in Python. Below are two different matrices; A and R. When changing the content of a single cell I am successful in the R-matrix, but not so much in the A-matrix, as the value-input affect the entire column and not only the single cell. Why does this happen? I would prefer the A-style of declaring the matrix.

n=6

A = [[0]*n]*n    
R=[[0,0,0,0,0,0], [0,0,0,0,0,0], [0,0,0,0,0,0], [0,0,0,0,0,0], [0,0,0,0,0,0], [0,0,0,0,0,0]]

R[1][1]=5
A[1][1]=5

print(R)
print(A)

The output from the two operations is:

[[0, 0, 0, 0, 0, 0], [0, 5, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0]]
[[0, 5, 0, 0, 0, 0], [0, 5, 0, 0, 0, 0], [0, 5, 0, 0, 0, 0], [0, 5, 0, 0, 0, 0], [0, 5, 0, 0, 0, 0], [0, 5, 0, 0, 0, 0]]

The `*` operator on a list creates a list of references to the same list. — Klaus D., Jan 07 '20 at 15:24

score 1 · Accepted Answer · answered Jan 07 '20 at 15:26

1

A = [[0]*n]*n creates multiple copies of the same list. This is why changing one affects every other one

answered Jan 07 '20 at 15:26

Mayowa Ayodele

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Thanks. Is there a fix for it? – Enthuziast Jan 07 '20 at 15:27
1

@Enthuziast Please see the linked duplicate. This question has already been asked+answered before – sshashank124 Jan 07 '20 at 15:29

Array-declaration issue in Python

1 Answers1