title: Python zero as file parameter in open function
body: <p>I'm currently puzzling around this piece of code.</p>
  <p>What exactly does</p>
  <pre class="lang-py prettyprint-override"><code>open(0)
  </code></pre>
  <p>do?</p>
  <p>I already looked up the docs or tried to find something in the internet but no clues.</p>
  <p>The codesnippet where this code is used:</p>
  <pre class="lang-py prettyprint-override"><code>map(abs,map(int,open(0).read().split()))
  </code></pre>
  <p>Thanks ^</p>