least_busy(backends, reservation_lookahead=60)[source]

Return the least busy backend from a list.

Return the least busy available backend for those that have a pending_jobs in their status. Note that local backends may not have this attribute.

  • backends (List[BaseBackend]) – The backends to choose from.

  • reservation_lookahead (Optional[int]) – A backend is considered unavailable if it has reservations in the next n minutes, where n is the value of reservation_lookahead. If None, reservations are not taken into consideration.

Return type



The backend with the fewest number of pending jobs.


IBMQError – If the backends list is empty, or if none of the backends is available, or if a backend in the list does not have the pending_jobs attribute in its status.