title: Save number of numy arrays as one matrix in npy
body: <p>I have result of some function as numpy of 8*1024. I need to save large number of such results in npy as one matrix. One way I could do is:</p>
  
  <pre><code>result []
  for input in range(inputs):    
      arr = computer (input) # arr = 8*1024
      result.append(arr)
  # After loop completes, save results 
  np.save('result.npy', result)
  </code></pre>
  
  <p>If I append all results in "result", it is on RAM so RAM goes to 100% in use. I need to save 'arr' in npy as it gets computed.
  Later, in order to do further processing, I load npy as given below, here I need to load results in random pattern:</p>
  
  <pre><code>result_load = np.load ('result.npy, mmap_mode='r)
  x = results[i] # i is some arbitrary random index
  final_result = algo_n(x)
  </code></pre>
  
  <p>Here, due to directly accessing from disk, I don't need too much RAM, however, in first part I can't find any way to save all array with out using too much RAM.</p>
  
  <p>Note: I have to do both processing separately as I have to try multiple algos on "x"     </p>