title: Set default value for selectbox
body: <p>I am new to streamlit.
  I tried to set a default value for sidebar.selectbox.
  The code is below.
  I appreciate the help!
  Thank you in advance.</p>
  <pre><code>st.sidebar.header('Settings')
  
  fichier = st.sidebar.selectbox('Dataset', ('djia', 'msci', 'nyse_n', 'nyse_o', 'sp500', 'tse'))
  
  window_ANTICOR = st.sidebar.selectbox('Window ANTICOR', ['&lt;select&gt;',3, 5, 10, 15, 20, 30])
  if window_ANTICOR == '&lt;select&gt;':    
      window_ANTICOR == 30
  
  window_OLMAR = st.sidebar.selectbox('Window OLMAR', ['&lt;select&gt;',3, 5, 10, 15, 20, 30])
  if window_OLMAR == '&lt;select&gt;':    
      window_OLMAR == 5
  
  eps_OLMAR = st.sidebar.selectbox('Eps OLMAR', ['&lt;select&gt;', 3, 5, 10, 15, 20, 30])
  if eps_OLMAR == '&lt;select&gt;':    
      eps_OLMAR == 10
  
  eps_PAMR = st.sidebar.selectbox('Eps PAMR', ['&lt;select&gt;',0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1])
  if eps_PAMR == '&lt;select&gt;':    
      eps_PAMR == 0.5
  
  variant = st.sidebar.selectbox('Variant PAMR', (0, 1, 2))
  if variant == '&lt;select&gt;':    
      eps_PAMR == 0
  </code></pre>