title: min, max and mean over large NumPy arrays in Python
body: <p>I have a very large NumPy array: <code>a = np.array</code>. From this array I want to get the min, max and average which can be easily done with <code>np.min(a)</code>, <code>np.max(a)</code> and <code>np.mean(a)</code>.</p>
  
  <p>However, I want also to have the min, max and average of a portion (begin part or end part) of this array. Are there some functions for this without creating a new array/list (because that would really result in a bad performance penalty)?</p>