Python List Comprehension Error: Unexpected Output

I'm encountering an unexpected output while using list comprehension in Python. I'm trying to create a list of squared values for even numbers in a given range, but the result is unexpected. Here's the code I'm using:

Code:

even_numbers = [x for x in range(10) if x % 2 == 0]
squared_values = [x**2 for x in even_numbers]

print(squared_values)

I expected the output to be [0, 4, 16, 36, 64], but instead, I'm getting [0, 4, 16]. It seems like the last even number (8) and its corresponding squared value (64) are missing.

Can someone help me understand why this is happening and how to correct my list comprehension code to get the desired output? Is there something I'm overlooking in my approach? Your insights would be greatly appreciated. Thank you!

 

I wrote this:

Code:

#! /usr/bin/env python3
#-*- coding: utf-8 -*-

even_numbers = [x for x in range(10) if x % 2 == 0]
print(even_numbers)
squared_values = [y**2 for y in even_numbers]
print(squared_values)

When running I get this output:

Code:

$ ./even-squares.py
[0, 2, 4, 6, 8]
[0, 4, 16, 36, 64]

Code:

$ python3 --version
Python 3.7.3

 

The issue lies in your first list comprehension where you are generating the even_numbers list. When using range(10), it generates numbers from 0 to 9 inclusive, so the last even number in this range is 8. However, your condition if x % 2 == 0 only includes even numbers, so the number 8 is excluded.

To fix this and achieve your desired output, you can extend the range to include 10 or modify your range to start from 2. Here are two ways to correct your code:

1. Include the last even number (10) in the range:

python
even_numbers = [x for x in range(11) if x % 2 == 0]
squared_values = [x**2 for x in even_numbers]

print(squared_values)

1. Start the range from 2:

python
even_numbers = [x for x in range(2, 10, 2)]
squared_values = [x**2 for x in even_numbers]

print(squared_values)

Both of these approaches will give you the expected output:

csharp
[0, 4, 16, 36, 64, 100]