input: Write a function to read an array from the user and then determine the mean and median of the array.
  
  def mean_median(arr): 
        arr_sum = 0 
        for i in range(len(arr)): 
              arr_sum += arr[i] 
        
        mean = arr_sum/len(arr) 
      
        arr = sorted(arr) 
        if len(arr) % 2 != 0: 
              median = arr[floor(len(arr)/2)] 
        else: 
              median = (arr[len(arr)//2] + arr[len(arr)//2 - 1]) / 2
        
        return mean, median
  
  assert mean_median([10, 15, 20, 25, 30, 35]) == (22.5, 22.5)
  assert mean_median([5, 3, 1, 2, 4]) == (3.0, 3)
  assert mean_median([4, 8, 6, 5, 9]) == (6.4, 6)
  assert mean_median([]) == (None, None)
  assert mean_median([100, 200, 300]) == (200.0, 200)
output: def mean_median(arr): 
      if not arr:
          return None, None
      
      arr_sum = 0 
      for i in range(len(arr)): 
          arr_sum += arr[i] 
      
      mean = arr_sum / len(arr) 
      
      arr = sorted(arr) 
      if len(arr) % 2 != 0: 
          median = arr[len(arr) // 2] 
      else: 
          median = (arr[len(arr) // 2] + arr[len(arr) // 2 - 1]) / 2
      
      return mean, median