title: What is this "score" actually? extra trees classifier with sklearn/Python
body: <p>I use <code>ExtraTreesClassifier</code> to find out which attributes are more important in my dataset. As a result, it returns me a score value (for example every attribute has a score like <code>0.037</code>, <code>0.025</code>, <code>0.012</code> etc..), what exactly does this score mean?</p>
  
  <p><strong>Edited: I am actually searching how is it calculating? Which formula gives me score?</strong></p>
  
  <pre><code>model = ExtraTreesClassifier()
  model.fit(dataValues, dataTargetEncoded)
  
  feat_importances = pd.Series(model.feature_importances_,index=dataValues.columns)
  feat_importances.nlargest(25).plot(kind='barh')
  plt.show()
  </code></pre>