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GO Classes DPP | GATE DA | Python Programming | Shallow Copy

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2 2 votes

Consider the following Python code:

matrix = [[1, 2], [3, 4]]
copy_matrix = matrix[:]

copy_matrix[0][1] = 99
copy_matrix[1] = [7, 8]

print(matrix, copy_matrix)

What is the output of the code above?

  1. [[1, 2], [3, 4]] [[1, 99], [7, 8]]
  2. [[1, 99], [7, 8]] [[1, 99], [7, 8]]
  3. [[1, 99], [3, 4]] [[1, 99], [7, 8]]
  4. [[1, 2], [7, 8]] [[1, 99], [7, 8]]

1 Answer

0 0 votes

The statement $\texttt{copy\_matrix = matrix[:]}$ creates a shallow copy of the outer list.

This means $\texttt{matrix}$ and $\texttt{copy\_matrix}$ are different outer lists, but the inner lists are still shared.

So $\texttt{copy\_matrix[0][1] = 99}$ changes the first inner list, which is shared by both outer lists.

matrix = [[1, 99], [3, 4]]

Then $\texttt{copy\_matrix[1] = [7, 8]}$ replaces only the second element of $\texttt{copy\_matrix}$ with a new list.

It does not change $\texttt{matrix[1]}$.

Therefore, the output is:

[[1, 99], [3, 4]] [[1, 99], [7, 8]]

Correct Option: C

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