code: def fibonacci_iterative(n):
      
      a, b = 0, 1
      for _ in range(0, n):
          a, b = b, a + b
      return a
docs: Args:
          n (int):
  
      Returns:
          int: the n-th fibonacci number
  
      References:
          http://stackoverflow.com/questions/15047116/iterative-alg-fib
  
      CommandLine:
          python -m utool.util_alg fibonacci_iterative
  
      Example:
          >>> # ENABLE_DOCTEST
          >>> from utool.util_alg import *  # NOQA
          >>> import utool as ut
          >>> with ut.Timer('fib iter'):
          >>>     series = [fibonacci_iterative(n) for n in range(20)]
          >>> result = ('series = %s' % (str(series[0:10]),))
          >>> print(result)
          series = [0, 1, 1, 2, 3, 5, 8, 13, 21, 34]