from multiprocessing import Pool
import time

class Sensor_A:
    def __init__(self):
        self.measurement_interval = 2
    def get_data(self):
        time.sleep(0.75)
        return 1

class Sensor_B:
    def __init__(self):
        self.measurement_interval = 3
    def get_data(self):
        time.sleep(0.6)
        return 2

def worker(obj):
    if not obj:
        return None
    else:
        return getattr(obj, 'get_data')()

def measure(n, sensor_list, interval):
    for i in range(0, n):
        start_time = time.time()
        measure_sensors = [ sensor
                            if i%sensor.measurement_interval==0
                            else None
                            for sensor in sensor_list ]
        with Pool(4) as p:
            results = p.map(worker, measure_sensors)
            waittime = (start_time
                    + interval
                    - time.time())
        time.sleep(waittime)
        print('{} at {}'.format(repr(results), time.time()))

if __name__=='__main__':
    sensor_list = [ Sensor_A(), Sensor_B(), Sensor_B() ]
    measure(5, sensor_list, 1)