title: AttributeError: 'GridSearchCV' object has no attribute 'cv_results_' on scikit-learn 0.19.2
body: <p>I'm currently using Scikit-Learn version 0.19.2 and Python 3.6.3</p>
  
  <p>For some reason, I can't access the <code>cv_results_</code> attribute from my <code>GridSearchCV</code>.</p>
  
  <p>This is the code I'm using:</p>
  
  <pre><code>df = pd.read_csv(input_file, sep = ";", header=None)
  
  numpy_array = df.as_matrix()
  y=numpy_array[:,1]
  y[y=='RR']=1
  y[y=='AIRR']=0
  print(y)
  y=y.astype('int')
  
  vectorizer = TfidfVectorizer(sublinear_tf=True, max_df=0.5, stop_words=stopwords)
  
  X=numpy_array[:,0]
  X=vectorizer.fit_transform(X)
  
  param_grid = {"base_estimator__criterion" : ["gini", "entropy"],
                "base_estimator__splitter" :   ["best", "random"],
                "n_estimators": [1, 2]
               }
  
  DTC = DecisionTreeClassifier(random_state = 11, max_features = "auto", class_weight = "balanced",max_depth = None)
  
  
  # Create and fit an AdaBoosted decision tree
  bdt = AdaBoostClassifier(base_estimator = DTC)
  
  grid_search_ABC = GridSearchCV(bdt, param_grid=param_grid, scoring = 'roc_auc', cv=5, refit=True)
  
  pred = grid_search_ABC.fit(X,y)
  
  print(metrics.confusion_matrix(y, pred))
  
  mean=grid_search_ABC.cv_results_['mean_test_score']
  std=grid_search_ABC.cv_results_['std_test_score']
  </code></pre>
  
  <p>I read that this has mostly to do with <code>GridSearchCV</code> not being fitted probably, but I can totally use it to predict new instances and etc.</p>
  
  <p>Any pointers, please?</p>