title: Why can't I do a loop in sys.stdin two times in a row ? (Python)
body: <p>First i need to get the number of lines and so i do :</p>
  
  <pre><code>for line in sys.stdin:
      c = c + 1
  print("Number of lines:" + str(c))
  A = [[] for x in range(0,c)]
  print(A)
  </code></pre>
  
  <p>But then I need to enter again a <code>for line in sys.stdin:</code> because I need to read the input.</p>
  
  <p>It does not work and the second time it is almost as the input was consumed and now is empty.</p>