title: AttributeError: 'GridSearchCV' object has no attribute 'best_params_'
body: <p>Grid search is a way to find the best parameters for any model out of the combinations we specify. I have formed a grid search on my model in the below manner and wish to find best parameters identified using this gridsearch.</p>
  
  <pre><code>from sklearn.model_selection import GridSearchCV
  # Create the parameter grid based on the results of random search 
  param_grid = {
      'bootstrap': [True],'max_depth': [20,30,40, 100, 110],
      'max_features': ['sqrt'],'min_samples_leaf': [5,10,15],
      'min_samples_split': [40,50,60], 'n_estimators': [150, 200, 250]
  }
  # Create a based model
  rf = RandomForestClassifier()
  # Instantiate the grid search model
  grid_search = GridSearchCV(estimator = rf, param_grid = param_grid, 
                            cv = 3, n_jobs = -1, verbose = 2)
  </code></pre>
  
  <p>Now I want to find the best parameters of the gridsearch as the output</p>
  
  <pre><code>grid_search.best_params_
  </code></pre>
  
  <p><strong>Error</strong>:</p>
  
  <pre><code>----&gt; grid_search.best_params_
  AttributeError: 'GridSearchCV' object has no attribute 'best_params_'
  </code></pre>
  
  <p>What am I missing?</p>