Super newbie trying to understand certain concepts

[perfringo]

In addition to newbieAuggie2019 thorough answer - print() is cheap way to understand what is going on:

In [1]: lst = [1, 2, 3] 
   ...: for v in range(len(lst)): 
   ...:     print(lst)                 # lst before insert
   ...:     lst.insert(1, lst[v]) 
   ...:     print(lst)                 # lst after insert
   ...:                                                                                         
[1, 2, 3]             
[1, 1, 2, 3]
[1, 1, 2, 3]
[1, 1, 1, 2, 3]
[1, 1, 1, 2, 3]
[1, 1, 1, 1, 2, 3]