title: Some strange behavior Python list and dict
body: <p>Can anyone explain why this happened with list and how to clean list after appending to another list?</p>
  
  <pre><code>&gt;&gt;&gt; t = {}
  &gt;&gt;&gt; t["m"] = []
  &gt;&gt;&gt; t
  {'m': []}
  &gt;&gt;&gt; t["m"].append('qweasdasd aweter')
  &gt;&gt;&gt; t["m"].append('asdasdaf ghghdhj')
  &gt;&gt;&gt; t
  {'m': ['qweasdasd aweter', 'asdasdaf ghghdhj']}
  &gt;&gt;&gt; r = []
  &gt;&gt;&gt; r.append(t)
  &gt;&gt;&gt; r
  [{'m': ['qweasdasd aweter', 'asdasdaf ghghdhj']}]
  &gt;&gt;&gt; t["m"] = []
  &gt;&gt;&gt; r
  [{'m': []}]
  </code></pre>