improve pickle load/dump practices

Use “with” syntax to load/dump final project pickles to make sure they
are properly closed after use.

final_project/poi_id.py

@@ -13,7 +13,8 @@
 features_list = ['poi','salary'] # You will need to use more features
 
 ### Load the dictionary containing the dataset
-data_dict = pickle.load(open("final_project_dataset.pkl", "r") )
+with open("final_project_dataset.pkl", "r") as data_file:
+    data_dict = pickle.load(data_file)
 
 ### Task 2: Remove outliers
 ### Task 3: Create new feature(s)

final_project/tester.py

@@ -78,14 +78,20 @@ def test_classifier(clf, dataset, feature_list, folds = 1000):
 FEATURE_LIST_FILENAME = "my_feature_list.pkl"
 
 def dump_classifier_and_data(clf, dataset, feature_list):
-    pickle.dump(clf, open(CLF_PICKLE_FILENAME, "w") )
-    pickle.dump(dataset, open(DATASET_PICKLE_FILENAME, "w") )
-    pickle.dump(feature_list, open(FEATURE_LIST_FILENAME, "w") )
+    with open(CLF_PICKLE_FILENAME, "w") as clf_outfile:
+        pickle.dump(clf, clf_outfile)
+    with open(DATASET_PICKLE_FILENAME, "w") as dataset_outfile:
+        pickle.dump(dataset, dataset_outfile)
+    with open(FEATURE_LIST_FILENAME, "w") as featurelist_outfile:
+        pickle.dump(feature_list, featurelist_outfile)
 
 def load_classifier_and_data():
-    clf = pickle.load(open(CLF_PICKLE_FILENAME, "r") )
-    dataset = pickle.load(open(DATASET_PICKLE_FILENAME, "r") )
-    feature_list = pickle.load(open(FEATURE_LIST_FILENAME, "r"))
+    with open(CLF_PICKLE_FILENAME, "r") as clf_infile:
+        clf = pickle.load(clf_infile)
+    with open(DATASET_PICKLE_FILENAME, "r") as dataset_infile:
+        dataset = pickle.load(dataset_infile)
+    with open(FEATURE_LIST_FILENAME, "r") as featurelist_infile:
+        feature_list = pickle.load(featurelist_infile)
     return clf, dataset, feature_list
 
 def main():