Ok, missed some requirements, so time for the next iteration 
Let’s try another simple solution. RuuviTagSensor.get_datas should return all advertised data, so let’s use that and pretty much same handling as previous solution had. Still can’t verify that this works, but if previous one did, maybe this one will also.
all_data = {}
last_clean = datetime.now()
def handle_data(new_data):
current_time = datetime.now()
key = new_data[0]
value = new_data[1]
if key not in all_data or all_data[key]['data'] != value:
all_data[key] = {'data': value, 'timestamp': current_time}
# TODO: Insert new_data to DB etc.
# Do not check all datas with every handle_data call
global last_clean
if last_clean < current_time:
last_clean = current_time
not_found = [key for key, value in all_data.items() if value['timestamp'] < current_time - timedelta(minutes=10)]
for key in not_found:
# TODO: Notify of lost sensors
del all_data[key]
RuuviTagSensor.get_datas(handle_data)
Performance wise this is not the best solution as writing to db can be slow, but let’s hope that db writes are fast Also cleanup is in the same handle_data function, so it is an ugly solution, but maybe for now we can live with that.