title: Python Context Manager to restore a variable's value?
body: <p>How would you write a context manager to restore a variable to its original value? For example:</p>
  
  <pre><code>x = 5
  with Restorer(x):
     x = 6
     ...
  print(x)
  </code></pre>
  
  <p>Output would be:
       5</p>