Explore Python list slicing with step values. Learn how a[::2] works and its output in this PCEP-30-02 exam question breakdown.
Table of Contents
Question
What will be the output of the following code snippet?
a = [1, 2, 3, 4, 5, 6, 7, 8, 9] print(a[::2])
A. [1, 3, 5, 7, 9]
B. [8, 9]
C. [1, 2, 3]
D. [1, 2]
Answer
The correct output of the given code snippet is:
A. [1, 3, 5, 7, 9]
Explanation
This question tests your understanding of Python list slicing, particularly the use of the step value in slice notation. Let’s break down the code:
- a = [1, 2, 3, 4, 5, 6, 7, 8, 9]
This creates a list ‘a’ with elements from 1 to 9. - print(a[::2])
This is where the slicing occurs. The slice notation has three parts: [start:stop:step]
– start: If omitted, it defaults to the beginning of the list
– stop: If omitted, it defaults to the end of the list
– step: Determines the increment between each item in the slice
In this case, a[::2] can be interpreted as:
- start is omitted, so it starts from the beginning (index 0)
- stop is omitted, so it goes until the end of the list
- step is 2, meaning it takes every second element
Therefore, the slice starts with the first element (1), skips one element, takes the third element (3), skips one, and so on. This results in selecting elements at indices 0, 2, 4, 6, and 8, which correspond to the values [1, 3, 5, 7, 9].
This slicing technique is powerful for selecting subsequences from lists with a regular pattern. It’s essential to understand for both the PCEP-30-02 exam and practical Python programming.
Python Institute PCEP-30-02 certification exam practice question and answer (Q&A) dump with detail explanation and reference available free, helpful to pass the Python Institute PCEP-30-02 exam and earn Python Institute PCEP-30-02 certification.