The last operator returns the last item emitted on the source observable. The following figure shows its marble diagram:

Its prototype is the following:

last(self, predicate=None)

Here, predicate is an optional function used to filter items in the source observable. If no predicate is provided, the last item of the observable is emitted.

Here is an example of this operator:

numbers = Observable.from_([1, 2, 3, 4, 5, 6])
numbers.last().subscribe(
    on_next = lambda i: print("on_next {}".format(i)),
    on_error = lambda e: print("on_error: {}".format(e)),
    on_completed = lambda: print("on_completed")
)

This gives the following result:

on_next 6
on_completed