title: Check if value is in Pandas dataframe column
body: <p>I've having an issue checking is a value is in the following dataframe:</p>
  <div class="s-table-container">
  <table class="s-table">
  <thead>
  <tr>
  <th>index</th>
  <th>open</th>
  <th>high</th>
  <th>SignalEMA25M50M</th>
  <th>PositionEMA25M50M</th>
  </tr>
  </thead>
  <tbody>
  <tr>
  <td>2021-03-30 05:35:00</td>
  <td>0.000059</td>
  <td>0.000059</td>
  <td>0</td>
  <td>-1.0</td>
  </tr>
  <tr>
  <td>2021-03-30 05:40:00</td>
  <td>0.000059</td>
  <td>0.000059</td>
  <td>0</td>
  <td>0.0</td>
  </tr>
  <tr>
  <td>2021-03-30 05:45:00</td>
  <td>0.000059</td>
  <td>0.000059</td>
  <td>0</td>
  <td>0.0</td>
  </tr>
  </tbody>
  </table>
  </div>
  <p>i am trying to simply return true if the PositionEMA25M50M contains -1.0</p>
  <p>i have tried:</p>
  <pre><code>if -1.0 in indicator_5min_df.PositionEMA25M50M:
      print('true')
  else:
      print('false')
  </code></pre>
  <p>however this returns false every time... i assume this is something to do with PositionEMA25M50M being of type float64 however i've also tried</p>
  <pre><code>if np.float64(-1.0) in indicator_5min_df.PositionEMA25M50M:
      print('true')
  else:
      print('false')
  </code></pre>
  <p>which has given me the same result...</p>
  <p>any ideas how i can fix this?</p>