title: Setting a Plotly Dash dcc.dropdown value dynamically
body: <p>Im building a plotly Dash <code>dcc.dropdown</code> list dynamically using :</p>
  
  <pre><code>def BuildOptions(DataFrameSeries, AddAll):  
      OptionList = [{'label': i, 'value': i} for i in DataFrameSeries.unique()]
      if AddAll == 1:       
          OptionList.insert(0,{'label': 'All', 'value': 'All'})          
      return OptionList
  </code></pre>
  
  <p>it uses unique values in a <code>df</code> series, and inserts 'All' into the options list. I now want to Set the (default) value to 'All' if it exists or the [0] item in the list of K/V pairs. </p>
  
  <pre><code>    html.Div([
              dcc.Dropdown(
                  id='Prov_DD',                    
                  options=BuildOptions(data.TASKPROVINCE,1),
                 # value=data.TASKPROVINCE[0],
                 # value=dcc.Dropdown.value[0],
                   value='All'  # this works for those list that have 'All' 
                                # but I want [0] item   
                  multi=True
              )],className='two columns'
              ),
  </code></pre>
  
  <p>Any way of setting the <code>dcc</code> drop down to a certain item in the options list of key value pairs by index?</p>