Python Comprehensions (ListDictSet) - Practice Question 2026 - Free Online Course

Master the art of Pythonic code with the most comprehensive practice exams dedicated to List, Dictionary, and Set Comprehensions. This course is designed to bridge the gap between knowing the syntax and writing high-performance, elegant Python code used by industry professionals.

Why Serious Learners Choose These Practice Exams

Serious learners understand that Python comprehensions are more than just "shorthand." They are essential for memory efficiency and readability. These practice exams are crafted to challenge your logic and improve your debugging skills. Unlike generic quizzes, our question bank focuses on edge cases, nested structures, and performance optimization, ensuring you can handle any Pythonic challenge in a technical interview or a production environment.

Course Structure

The curriculum is strategically divided into six focused modules to ensure a smooth learning curve:

Basics / Foundations: This section focuses on the fundamental syntax of list comprehensions. You will practice converting simple for-loops into single-line expressions and understand the basic "output-expression + iteration" structure.
Core Concepts: Here, we introduce conditional logic using "if" statements within comprehensions. You will learn how to filter data effectively across lists, sets, and dictionaries while maintaining clean code.
Intermediate Concepts: This module dives into dictionary and set comprehensions. You will master key-value mapping and the unique property of sets to handle distinct elements, along with handling multiple transformations in a single line.
Advanced Concepts: Learn to tackle complexity with nested comprehensions and multiple for-clauses. This section covers flattening multidimensional arrays and creating complex data structures efficiently.
Real-world Scenarios: Apply your knowledge to practical data processing tasks. These questions simulate real-world problems like cleaning JSON-like dictionaries, parsing logs, and formatting data for analysis.
Mixed Revision / Final Test: A comprehensive final evaluation that mixes all difficulty levels. This simulates a real exam environment to test your speed, accuracy, and overall retention of Pythonic principles.

Sample Practice Questions

Question 1

What is the output of the following code?

{x: x**2 for x in [1, 2, 2, 3] if x % 2 != 0}

Option 1: {1: 1, 2: 4, 3: 9}
Option 2: {1: 1, 3: 9}
Option 3: [1, 9]
Option 4: {1, 9}
Option 5: Error

Correct Answer: Option 2

Correct Answer Explanation: This is a dictionary comprehension. It iterates through the list [1, 2, 2, 3]. The condition if x % 2 != 0 filters out even numbers, leaving only 1 and 3. The expression {x: x**2} creates a key-value pair where the key is the number and the value is its square. Thus, the result is {1: 1, 3: 9}.

Wrong Answers Explanation:

Option 1: Incorrect because the number 2 is even and is filtered out by the if x % 2 != 0 condition.
Option 3: Incorrect because the curly braces {} and the colon : denote a dictionary comprehension, not a list comprehension.
Option 4: Incorrect because this is the syntax for a set comprehension, but the code provided uses key-value pairs (colon syntax).
Option 5: Incorrect because the syntax is perfectly valid Python.

Question 2

Which of the following creates a set of all unique first letters from the list: ['apple', 'banana', 'apricot']?

Option 1: [word[0] for word in ['apple', 'banana', 'apricot']]
Option 2: {word[0] for word in ['apple', 'banana', 'apricot']}
Option 3: {word: word[0] for word in ['apple', 'banana', 'apricot']}
Option 4: (word[0] for word in ['apple', 'banana', 'apricot'])
Option 5: set([word for word in ['apple', 'banana', 'apricot']])

Correct Answer: Option 2

Correct Answer Explanation: Option 2 uses set comprehension syntax {expression for item in iterable}. Since sets automatically handle uniqueness, the two 'a' characters from 'apple' and 'apricot' are reduced to a single 'a', resulting in {'a', 'b'}.

Wrong Answers Explanation:

Option 1: This is a list comprehension. While it gets the first letters, it allows duplicates and returns a list ['a', 'b', 'a'].
Option 3: This is a dictionary comprehension. It creates a mapping of the full word to its first letter rather than a set of letters.
Option 4: This creates a generator object, not a set.
Option 5: This creates a set of the full words, not the first letters of those words.

Course Features

Welcome to the best practice exams to help you prepare for your Python Comprehensions (ListDictSet) .