How to get index of the last item with a given value

Question

In a list of integer values

a = [4, 8, 2, 3, 8, 5, 8, 8, 1, 4, 8, 2, 1, 3]

I have to find the index of the last item with value 8. Is there more elegant way to do that rather than mine:

a = [4, 8, 2, 3, 8, 5, 8, 8, 1, 4, 8, 2, 1, 3]

for i in range(len(a)-1, -1, -1):
    if a[i] == 8:
        print(i)
        break

Possible duplicate of [How to find the last occurrence of an item in a Python list](https://stackoverflow.com/questions/6890170/how-to-find-the-last-occurrence-of-an-item-in-a-python-list) — Aniket Navlur, Oct 21 '18 at 09:35

score 4 · Answer 1 · answered Oct 21 '18 at 09:19

4

Try This:

a = [4, 8, 2, 3, 8, 5, 8, 8, 1, 4, 8, 2, 1, 3]
index = len(a) - 1 - a[::-1].index(8)

Just reverse the array and find first index of element and then subtract it from length of array.

answered Oct 21 '18 at 09:19

Rohit-Pandey

score 1 · Answer 2 · answered Oct 21 '18 at 09:25

1

>>> lst = [4, 8, 2, 3, 8, 5, 8, 8, 1, 4, 8, 2, 1, 3]
>>> next(i for i in range(len(lst)-1, -1, -1) if lst[i] == 8)
10

This throws StopIteration if the list doesn't contain the search value.

answered Oct 21 '18 at 09:25

Aran-Fey

score 0 · Answer 3 · answered Oct 21 '18 at 17:02

0

Use sorted on all indexes of items with a value of 8 and take the last value, or using reverse = True take the first value

x = sorted(i for i, v in enumerate(a) if v == 8)[-1]

print(x) # => 10

answered Oct 21 '18 at 17:02

vash_the_stampede

3 Answers3