Python Coding Challange - Question With Answer(01231224)

 

What will be the output of the following code?

import numpy as np
arr = np.arange(1, 10).reshape(3, 3)
result = arr.sum(axis=0) - arr.sum(axis=1)
print(result)

[0, 0, 0]
[1, -1, 1]
[3, -3, 3]
[2, 2, -2]

Step 1: Create the array with np.arange(1, 10)

The function np.arange(1, 10) creates a 1D NumPy array containing integers from 1 to 9 (inclusive of 1 but exclusive of 10).

np.arange(1, 10) = [1, 2, 3, 4, 5, 6, 7, 8, 9]

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Step 2: Reshape the array to 3x3

The method .reshape(3, 3) converts the 1D array into a 2D array with 3 rows and 3 columns:

arr = [[1, 2, 3],
      [4, 5, 6],
      [7, 8, 9]]

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Step 3: Compute arr.sum(axis=0)

The parameter axis=0 means sum along columns (vertically).
For each column, we add the elements from the top to the bottom:

• First column: $1 + 4 + 7 = 12$
• Second column: $2 + 5 + 8 = 15$
• Third column: $3 + 6 + 9 = 18$

Result of arr.sum(axis=0):

[12, 15, 18]

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Step 4: Compute arr.sum(axis=1)

The parameter axis=1 means sum along rows (horizontally).
For each row, we add the elements from left to right:

• First row: $1 + 2 + 3 = 6$
• Second row: $4 + 5 + 6 = 15$
• Third row: $7 + 8 + 9 = 24$

Result of arr.sum(axis=1):

[6, 15, 24]

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Step 5: Perform element-wise subtraction

The subtraction operation is element-wise, meaning corresponding elements of the two arrays are subtracted.

• $12 - 6 = 6$
• $15 - 15 = 0$
• $18 - 24 = -6$

Result of arr.sum(axis=0) - arr.sum(axis=1):

[6, 0, -6]

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Step 6: Print the result

Finally, the result is printed:

[6, 0, -6]

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Key Points:

1. axis=0 computes the sum along columns (vertically).
2. axis=1 computes the sum along rows (horizontally).
3. Subtraction is performed element-wise between the two resulting arrays.