Given a 2D numpy array arr with shape (3, 3), which of the following expressions will extract the diagonal elements as a 1D array?

hard📝 Application Q9 of 15

NumPy - Indexing and Slicing

Given a 2D numpy array arr with shape (3, 3), which of the following expressions will extract the diagonal elements as a 1D array?

Aarr[range(3), range(3)]

Barr[:, 0]

Carr[0, :]

Darr[1, 1]

Step-by-Step Solution

Solution:

Step 1: Understand diagonal extraction
Diagonal elements have equal row and column indices: (0,0), (1,1), (2,2).
Step 2: Use indexing with matching row and column indices
arr[range(3), range(3)] selects elements at (0,0), (1,1), (2,2).
Final Answer:
arr[range(3), range(3)] -> Option A
Quick Check:
Matching row and column indices extract diagonal [OK]

Quick Trick: Use arr[range(n), range(n)] to get diagonal elements [OK]

Common Mistakes:

Master "Indexing and Slicing" in NumPy

9 interactive learning modes - each teaches the same concept differently

Want More Practice?

15+ quiz questions · All difficulty levels · Free

More NumPy Quizzes