title: Python del and garbage collecting
body: <p>First look at my Python code,</p>
  <pre><code>s = [[1, 2], [3, 6], [9, 6]]
  t = s
  i = s[0]
  
  del i
  del t[0]
  </code></pre>
  <p>There is three references for [2, 1]; t[0], s[0] and &quot;i&quot;, so if we try and delete of them it shouldn't effect on [1,2] because [1,2] still has two another reference so Python garbage-collection system doesn't
  remove [1,2] do to the having no reference. So why deleting &quot;i&quot; doesn't
  effect on [1,2] but deleting t[0] does.</p>