title: What is the difference between num[:] and num?
body: <pre><code>nums = []
  vals = nums
  vals.append(1)
  </code></pre>
  
  <p>the result shows nums and vals are of same length but</p>
  
  <pre><code>nums = []
  vals = nums[:]
  vals.append(1)
  </code></pre>
  
  <p>this shows vals is longer than num</p>