title: django modelchoicefield with distinct column values
body: <p>What I'd like to do is populate a <code>select</code> element with distinct values from one column in the model table.</p>
  
  <p>my forms.py:</p>
  
  <pre><code>class ExampleForm(forms.ModelForm):
      only_unique_values = forms.ModelChoiceField(
          required = False,
          queryset = ReadOnlyTable.objects.values('pie').distinct(),
          widget = forms.Select
      )
  </code></pre>
  
  <p>Using the <code>values</code> function returns a <code>ValuesQuerySet</code> instead of a <code>QuerySet</code>, which is a problem for my <code>select</code> element because all the options are populated with the dictionary syntax as the values instead of just the column data as <code>string</code>s.</p>
  
  <p><strong>It ends up looking like this</strong>:</p>
  
  <pre><code>&lt;select id="id_example" name="example_form"&gt;
  &lt;option value="" selected="selected"&gt;---------&lt;/option&gt;
  &lt;option value="{'pie': u'apple     '}"&gt;{'pie': u'apple     '}&lt;/option&gt;
  &lt;option value="{'pie': u'pecan     '}"&gt;{'pie': u'pecan     '}&lt;/option&gt;
  &lt;option value="{'pie': u'dutch     '}"&gt;{'pie': u'dutch     '}&lt;/option&gt;
  &lt;option value="{'pie': u'pumpkin     '}"&gt;{'pie': u'pumpkin     '}&lt;/option&gt;
  &lt;/select&gt;
  </code></pre>
  
  <p><strong>How I would want it to look is like so</strong>:</p>
  
  <pre><code>&lt;select id="id_example" name="example_form"&gt;
  &lt;option value="" selected="selected"&gt;---------&lt;/option&gt;
  &lt;option value="apple"&gt;apple&lt;/option&gt;
  &lt;option value="pecan"&gt;pecan&lt;/option&gt;
  &lt;option value="dutch"&gt;dutch&lt;/option&gt;
  &lt;option value="pumpkin"&gt;pumpkin&lt;/option&gt;
  &lt;/select&gt;
  </code></pre>
  
  <p><strong>How can I return <code>string</code> values from a <code>distinct()</code> call on my model?</strong></p>