title: Python multiple assignment and references
body: <p>Why does multiple assignment make distinct references for ints, but not lists or other objects?</p>
  
  <pre><code>&gt;&gt;&gt; a = b = 1
  &gt;&gt;&gt; a += 1
  &gt;&gt;&gt; a is b
  &gt;&gt;&gt;     False
  &gt;&gt;&gt; a = b = [1]
  &gt;&gt;&gt; a.append(1)
  &gt;&gt;&gt; a is b
  &gt;&gt;&gt;     True
  </code></pre>