import random


def rand_real(range_start, range_stop):
    """
    Generates a random real number by using random.random to generate a random x in [0,1)
    and transforming it to be y between range_start and range_stop: 
        y = x * (range_stop - range_start) + range_start
    """
    return random.random()*(range_stop - range_start) + range_start