Recursion in a tailored map function - don't understand the program flow

I am learning tail recursion and don't understand the flow of this example. I am using VSCode debugger and don't understand why when the program reaches return[f(arg), *result] it goes to result = my_map(f, rest) line and arg becomes 2

(attached picture VSCode Debugger - step I don't understand).

def my_map(f, iterable):
        arg, *rest = iterable
    except ValueError:
        return []
    result = my_map(f, rest)
    return[f(arg), *result]

print(my_map(lambda x: x+10, [1,2,3]))

I am not used to the unpack operator (*) so maybe I am missing something there.

Since arg was 3 and result was [], I was just expecting the return to return a list like [3,[]].

Title EDITED: it is not tail recursion since the recursion isn't the last thing the function does.- Thanks >

EDITED: more explanation about what I don't understand: First, I get everything until result becomes an empty list. looping through try-except block Then, we get into return [f(arg),*result] There is where I don't understand why the execution (seeing it from the debugger) goes back to the previous line (result). So if someone could explain me what is happening from that point on...


  • To understand the flow I had 1st to watch this ideal video about recursion Then I understood that it was not a good example to understand recursion at all...

    So based on that, I did the map of the call stack status in the same fashion it is done in the video. See picture: Call stack status

    Hope it helps