title: Python: change the first element to the list itself
body: <p>I have a list:</p>
  
  <pre><code>mylist = [1,2,3]
  </code></pre>
  
  <p>And I want to change the first element to the list, so a list inside a list.
  My first try:</p>
  
  <pre><code>mylist + mylist[1:]
  </code></pre>
  
  <p>gives me </p>
  
  <pre><code>[1, 2, 3, 2, 3] # not what I want
  </code></pre>
  
  <p>my second try</p>
  
  <pre><code>mylist[0]=mylist
  </code></pre>
  
  <p>gives me</p>
  
  <pre><code>[[...], 2, 3] # is this an infinite list?
  </code></pre>
  
  <p>Although I want</p>
  
  <pre><code>[[1,2,3], 2, 3]
  </code></pre>