import math
import random


def rand_scale_log_normal(mean_scale, one_sigma_at_scale):
    """
    Generate a distribution of value at log  scale around mean_scale

    :param mean_scale:  
    :param one_sigma_at_scale: 67% of values between  mean_scale/one_sigma_at_scale .. mean_scale*one_sigma_at_scale
    :return: 
    """

    log_sigma = math.log(one_sigma_at_scale)
    return mean_scale*math.exp(random.normalvariate(0.0, log_sigma))