text: #
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  # Called to generate a delay value
  
  import abc
  import random
  
  
  class Delay(object):
      __metaclass__ = abc.ABCMeta
  
      def __init__(self):
          pass
  
      @abc.abstractmethod
      def next(self):
          """
          Generate the next delay time in seconds
          :return: float (seconds)
          """
          pass
  
  
  class ExponentialDelay(Delay):
      """
      Generates a delay from an exponential distribution with the specified mean (1/lambda):
  
      TODO: Should generate its own seed and keep its own RNG stream
      """
  
      def __init__(self, min_delay, mean):
          """
          :param min_delay: Added to the exponential sample
          :param mean: the mean exponential delay (1 / lambda)
          """
          super(ExponentialDelay, self).__init__()
          if mean <= 0.0: raise ValueError("Mean must be positive, got {}".format(mean))
          self._beta = mean
          self._min = min_delay
  
      def next(self):
          return random.expovariate(1/self._beta) + self._min
  
  
  
  class UniformDelay(Delay):
      """
      TODO: Should generate its own seed and keep its own RNG stream
      """
  
      def __init__(self, lower, upper):
          super(UniformDelay, self).__init__()
          self._lower = lower
          self._upper = upper
  
      def next(self):
          return random.uniform(self._lower, self._upper)
  
  
  Delay.register(ExponentialDelay)
  Delay.register(UniformDelay)
  
  