index is meant to return the index of the first match it finds in the list from the beginning, it's most simpless implementation is: ``` for i, v in enumerate(self): if v == value: return i throw ValueError(f"Value '{value}' is not in list") ```` if you want the negative index, just subtract the list's length from the returned index: ``` res = listy.index(10) - len(listy) ```

On Fri, 29 Jan 2021 at 14:37, Francis O'Hara Aidoo <kofiohara@gmail.com> wrote:

I understand that the same effect can be achieved with the index notation - as in if listy[-1] == 10: print("Monty Python") - but the way that came naturally to me was to use the .index method rather than index notation, and it took a very long time for me to figure out why my code was not working(mostly because I'm a beginner). So do what you will, I guess.:)

Another issue here is that indexing and the list.index method are not meant to be equivalent. In particular, the list.index method has to test all the elements in your list before it finds the value you are looking for, while indexing will just look up at the position you asked for, which is much faster for long lists (especially since you are looking at the last element in the list). In general, you shouldn't be using list.index if you already know the index you are looking for.

Best, E

index is meant to return the index of the first match it finds in the list from the beginning, it's most simpless implementation is: ``` for i, v in enumerate(self): if v == value: return i throw ValueError(f"Value '{value}' is not in list") ```` if you want the negative index, just subtract the list's length from the returned index: ``` res = listy.index(10) - len(listy) ```

On Fri, 29 Jan 2021 at 14:37, Francis O'Hara Aidoo <kofiohara@gmail.com> wrote:

I understand that the same effect can be achieved with the index notation - as in if listy[-1] == 10: print("Monty Python") - but the way that came naturally to me was to use the .index method rather than index notation, and it took a very long time for me to figure out why my code was not working(mostly because I'm a beginner). So do what you will, I guess.:)

Another issue here is that indexing and the list.index method are not meant to be equivalent. In particular, the list.index method has to test all the elements in your list before it finds the value you are looking for, while indexing will just look up at the position you asked for, which is much faster for long lists (especially since you are looking at the last element in the list). In general, you shouldn't be using list.index if you already know the index you are looking for.

Best, E