How to filter list of dictionaries with matching values for a given key
<p>With an interface like <code>a = copyf(dictlist, key, valuelist)</code>.</p>

<pre><code>&gt;&gt;&gt; dictlist = [{'first': 'James',
                 'last': 'Joule'},
                {'first': 'James',
                 'last': 'Watt'},
                {'first': 'Christian',
                 'last': 'Doppler'}]
&gt;&gt;&gt; valuelist = ['James', 'John']
&gt;&gt;&gt; x = copyf(dictlist, 'first', valuelist)
&gt;&gt;&gt; print(x)
[{'first': 'James',
  'last': 'Joule'},
 {'first': 'James',
  'last': 'Watt'}]
</code></pre>

<p>The <code>dictlist</code> is effectively a <code>csv.DictReader</code> instance.</p>
