title: Mapping over values in a python dictionary
body: <p>Given a dictionary <code>{ k1: v1, k2: v2 ... }</code> I want to get <code>{ k1: f(v1), k2: f(v2) ... }</code> provided I pass a function <code>f</code>.</p>
  
  <p>Is there any such built in function? Or do I have to do</p>
  
  <pre><code>dict([(k, f(v)) for (k, v) in my_dictionary.iteritems()])
  </code></pre>
  
  <p>Ideally I would just write</p>
  
  <pre><code>my_dictionary.map_values(f)
  </code></pre>
  
  <p>or</p>
  
  <pre><code>my_dictionary.mutate_values_with(f)
  </code></pre>
  
  <p>That is, it doesn't matter to me if the original dictionary is mutated or a copy is created.</p>