6 – Last element that satisfies a condition

6 – Last element that satisfies a condition#

If you have a condition, you can get the last element of an iterable that satisfies that condition with collections.deque and a generator expression:

from collections import deque

last = deque(
    (elem for elem in iterable if condition(elem)),
    maxlen=1,
).pop()

If there are no such elements, the deque will be empty and popping gives an IndexError, so you may need to account for that. You can either

check if the deque has any elements before popping:

from collections import deque

important_numbers = [42, 10, 16, 0]
dq = deque((num for num in important_numbers if num % 2), maxlen=1)
if not dq:
    print("No odd numbers found!")
# No odd numbers found!

or you can handle the IndexError that you might get when popping:

from collections import deque

important_numbers = [42, 10, 16, 0]
try:
    last_odd = deque(
        (num for num in important_numbers if num % 2),
        maxlen=1,
    ).pop()
except IndexError:
    print("No odd numbers found!")
# No odd numbers found!