def RelativeChange(before, after):
  """Returns the absolute value of the relative change between two values.

  Args:
    before: First value.
    after: Second value.

  Returns:
    Relative change from the first to the second value, or infinity if the
    first value is zero. This is guaranteed to be non-negative.
  """
  return abs((after - before) / float(before)) if before else float('inf')