What is NumPy - Practice Questions & Exercises

Challenge - 5 Problems

🧠 Conceptual

intermediate

What is the primary purpose of NumPy?

NumPy is a popular Python library. What is its main use?

A To perform fast numerical computations with arrays and matrices.

B To create interactive web pages.

C To manage databases and SQL queries.

D To build machine learning models without data preprocessing.

💡 Hint

Think about what kind of data structure NumPy mainly works with.

NumPy provides efficient tools to work with arrays and matrices, enabling fast numerical calculations.

❓ Predict Output

intermediate

What is the output of this NumPy code?

Look at the code below. What will it print?

NumPy

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

A [1 2 3 1 2 3]

B TypeError: unsupported operand type(s) for *: 'list' and 'int'

C [3 4 5]

D [2 4 6]

💡 Hint

Multiplying a NumPy array by a number multiplies each element.

NumPy arrays support element-wise operations. Multiplying by 2 doubles each element.

❓ data_output

advanced

What is the shape of the resulting NumPy array?

Consider this code creating a 2D array. What is the shape of arr?

NumPy

import numpy as np
arr = np.array([[1, 2, 3], [4, 5, 6]])
print(arr.shape)

A (1, 6)

B (6,)

C (2, 3)

D (3, 2)

💡 Hint

Count rows and columns in the nested list.

The array has 2 rows and 3 columns, so its shape is (2, 3).

🔧 Debug

advanced

What error does this NumPy code raise?

What error will this code produce?

NumPy

import numpy as np
arr = np.array([1, 2, 3])
print(arr[3])

A IndexError: index 3 is out of bounds for axis 0 with size 3

B TypeError: 'int' object is not subscriptable

C ValueError: could not broadcast input array

D SyntaxError: invalid syntax

💡 Hint

Remember Python indexing starts at 0 and the last index is length-1.

Index 3 is out of range for an array of size 3 (indices 0,1,2).

🚀 Application

expert

Which option produces the correct mean of a NumPy array?

Given arr = np.array([1, 2, 3, 4, 5]), which code correctly calculates the mean?

NumPy

import numpy as np
arr = np.array([1, 2, 3, 4, 5])

A arr.sum() / arr.size

B all of the above

C np.mean(arr)

D arr.mean()

💡 Hint

Think about different ways to calculate average in NumPy.

All options A, B, and D correctly compute the mean of the array.