Python List: 10 Must-Know Interview Questions

Introduction

Python lists are one of the foundational data structures in Python and a topic that often comes up in technical interviews. To help you prepare, we’ve compiled a list of 10 commonly asked questions and their answers about Python lists.

Question:

Explain what a list is in Python and give an example.

Answer:

In Python, a list is an ordered collection of elements that can be of different data types. It is mutable, meaning you can change its content.

Example:

my_list = [1, 2.5, 'string', True]

Question:

How do you access the elements stored in a Python list?

Answer:

Elements in a list can be accessed using their index, starting from 0 for the first element.

Example:

my_list = [10, 20, 30]
print(my_list[0])  # Output: 10

Question:

What is slicing and how can you slice lists in Python?

Answer:

Slicing is the act of getting a subset of elements from an iterable based on the indices. You can slice a list using the syntax [start:stop:step].

Example:

my_list = [0, 1, 2, 3, 4, 5]
sliced_list = my_list[1:5:2]
print(sliced_list)  # Output: [1, 3]

Question:

How can you add elements to a Python list?

Answer:

Elements can be added to a list using methods like append(), extend(), and insert().

Example:

my_list = [1, 2, 3]
my_list.append(4)
print(my_list)  # Output: [1, 2, 3, 4]

Question:

How can you remove elements from a Python list?

Answer:

You can remove elements using methods like remove(), pop(), and clear().

Example:

my_list = [1, 2, 3]
my_list.remove(2)
print(my_list)  # Output: [1, 3]

Question:

How can you clone or copy a list in Python?

Answer:

You can clone a list using slicing, the copy() method, or the copy module.

Example:

new_list = my_list[:]

Question:

What is list comprehension and how is it used?

Answer:

List comprehension is a compact way to create lists. It can substitute for loops and append() method for creating lists.

Example:

squares = [x*x for x in range(5)]
print(squares)  # Output: [0, 1, 4, 9, 16]

Question:

How can you sort a list in Python?

Answer:

You can sort a list using the sort() method for in-place sorting or the sorted() function for creating a new sorted list.

Example:

my_list = [3, 1, 2]
sorted_list = sorted(my_list)
print(sorted_list)  # Output: [1, 2, 3]

Question:

How can you reverse a list in Python?

Answer:

You can reverse a list using the reverse() method or by using slicing with a step of -1.

Example:

my_list = [1, 2, 3]
my_list.reverse()
print(my_list)  # Output: [3, 2, 1]

Question:

What are nested lists in Python?

Answer:

In Python, you can have a list containing other lists, known as nested lists.

Example:

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

Conclusion

Understanding Python lists is crucial for any Python developer. The above questions are a good starting point to solidify your understanding and prepare you for Python interviews.