Negative indexing in NumPy - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to select the last element of the numpy array.

NumPy

import numpy as np
arr = np.array([10, 20, 30, 40, 50])
last_element = arr[1]

Drag options to blanks, or click blank then click option'

A[0]

B[1]

C[-1]

D[-5]

Attempts:

3 left

💡 Hint

Common Mistakes

Using positive index 1 instead of -1.

Using 0 which selects the first element.

Using -5 which selects the first element but is less clear.

Using arr[-1] selects the last element in the array.

2fill in blank

medium

Complete the code to select the second last element of the numpy array.

NumPy

import numpy as np
arr = np.array([5, 15, 25, 35, 45])
second_last = arr[1]

Drag options to blanks, or click blank then click option'

A[-2]

B[1]

C[-1]

D[2]

Attempts:

3 left

💡 Hint

Common Mistakes

Using positive index 2 which selects the third element.

Using -1 which selects the last element.

Using positive index 1 which selects the second element.

arr[-2] selects the second last element in the array.

3fill in blank

hard

Fix the error in the code to correctly select the last three elements using negative indexing.

NumPy

import numpy as np
arr = np.array([2, 4, 6, 8, 10, 12])
last_three = arr[1]

Drag options to blanks, or click blank then click option'

A[-3:]

B[:3]

C[3:]

D[-3]

Attempts:

3 left

💡 Hint

Common Mistakes

Using [:3] which selects first three elements.

Using [3:] which selects elements from index 3 to end but not negative indexing.

Using [-3] which selects only one element.

arr[-3:] selects the last three elements of the array.

4fill in blank

hard

Fill both blanks to create a dictionary with words as keys and their last two characters as values.

NumPy

words = ['apple', 'banana', 'cherry']
last_two_chars = {word: word[1] for word in words if len(word) [2] 2}

Drag options to blanks, or click blank then click option'

A[-2:]

B>

C<

D[:2]

Attempts:

3 left

💡 Hint

Common Mistakes

Using [:2] which gets first two characters.

Using length less than 2 which excludes longer words.

Using negative index without colon which selects single character.

The slice word[-2:] gets the last two characters. The condition len(word) > 2 ensures words are long enough.

5fill in blank

hard

Fill all three blanks to create a dictionary with uppercase words as keys and their last character as values, only for words longer than 3 letters.

NumPy

words = ['dog', 'elephant', 'cat', 'giraffe']
result = {word[1]: word[2] for word in words if len(word) [3] 3}

Drag options to blanks, or click blank then click option'

A.upper()

B[-1]

C>

D[:1]

Attempts:

3 left

💡 Hint

Common Mistakes

Using [:1] which gets first character instead of last.

Using length less than or equal to 3 which includes short words.

Not converting keys to uppercase.

word.upper() converts to uppercase keys, word[-1] gets last character, and len(word) > 3 filters words longer than 3 letters.