Python Coding Challange - Question With Answer(01201224)

 

What will be the output of the following code?

import numpy as np
arr = np.array([1, 2, 3, 4])
result = arr * arr[::-1]
print(result)

[1, 4, 9, 16]
[4, 6, 6, 4]
[4, 6, 6]
[4, 4, 4, 4]

Step 1: Create the NumPy array

The line:

arr = np.array([1, 2, 3, 4])

creates a 1D NumPy array:

arr = [1, 2, 3, 4]

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Step 2: Reverse the array using arr[::-1]

The slicing operation arr[::-1] reverses the array:

arr[::-1] = [4, 3, 2, 1]

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Step 3: Element-wise multiplication

In NumPy, when you multiply two arrays of the same shape, the multiplication is element-wise. This means each element in one array is multiplied by the corresponding element in the other array.

result = arr * arr[::-1]

Here:

arr       = [1, 2, 3, 4]
arr[::-1] = [4, 3, 2, 1]

Performing the element-wise multiplication:

result = [1*4, 2*3, 3*2, 4*1]
       = [4, 6, 6, 4]

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Step 4: Print the result

Finally:

print(result)

outputs:

[4, 6, 6, 4]

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Key Points:

1. arr[::-1] reverses the array.
2. Element-wise operations are default behavior in NumPy when performing arithmetic on arrays of the same size.
3. The multiplication here computes each element as arr[i] * arr[len(arr)-i-1]