Exam PCEP-30-02 topic 1 question 20 discussion

Let's analyze the given code step by step: Initial list: my_list = [1, 2] Loop: for v in range(2): my_list.insert(-1, my_list[v]) The loop runs two times (v = 0 and v = 1) because range(2) generates values 0 and 1. Inside the loop, the insert(-1, my_list[v]) method inserts my_list[v] into the second-to-last position (-1 index). Iteration Breakdown: Iteration 1 (v = 0): my_list[v] = my_list[0] = 1 insert(-1, 1) inserts the value 1 just before the last element. The list becomes: [1, 1, 2] Iteration 2 (v = 1): Now my_list = [1, 1, 2], so my_list[v] = my_list[1] = 1. insert(-1, 1) again inserts the value 1 before the last element. The list becomes: [1, 1, 1, 2] Final list: After both iterations, the list my_list becomes [1, 1, 1, 2]. Output: Thus, the output of print(my_list) is: [1, 1, 1, 2]

In Python, when using the insert() method with lists, the index -1 behaves differently from how negative indexing works for accessing elements. Negative index: With insert(-1, value), Python interprets -1 as "insert before the element at index -1". Since -1 refers to the last element for access, inserting before this position means the new element goes before the current last element, not at the very end. This might seem counterintuitive at first, but it's consistent with how Python treats indexing for modification versus access: Access: -1 gets you the last element. Insertion: -1 means insert just before where you would access with -1.

why is insert(-1, ...) mean insert at the second to last position? wouldn't insert(0, ...) insert at the first place as it's meant for 0 of index place? therefore, -1 is the last digit... is it not?

Let's step through this code to understand what's happening: We start with my_list = [1, 2] The loop for v in range(2): will run twice, with v taking values 0 and 1. In each iteration, we're using my_list.insert(-1, my_list[v]): insert(-1, ...) means insert at the second-to-last position my_list[v] is the element we're inserting Let's go through the iterations: First iteration (v = 0): We insert my_list[0] (which is 1) at index -1 my_list becomes [1, 1, 2] Second iteration (v = 1): We insert my_list[1] (which is now 1) at index -1 my_list becomes [1, 1, 1, 2] After the loop, we print my_list Therefore, the output will be: [1,1,1,2]

my_list = [1,2] for v in range (2): my_list.insert(-1,my_list[v]) >>> loop 1: v=0 >> insert my_list[0] in the position my_list[-1] >> my_list = [1,1,2] >>> loop 2: v=1 >> insert my_list[1] in the position my_list[-1] >> my_list = [1,1,1,2] print(my_list) >>>> [1,1,1,2] (B)

b is the correct answer