title: Python, what does [i for i] mean
body: <p>I just started learning python, I solved the problem but there's something that I dont quite understand. What does [i for i mean] in these sentence:</p>
  
  <pre><code>def sortByHeight(a):
      iL = [i for i, x in enumerate(a) if x == -1]
      print(iL)
      sL = list(filter(lambda b: b != -1, a))
      sL.sort()
  </code></pre>
  
  <p>Could anyone pls explain to me ?, thank you so much</p>