add __dir__ to bunch for better autocomplete (scikit-learn#7090)

Author: amueller

sklearn/datasets/base.py

@@ -51,6 +51,9 @@ def __init__(self, **kwargs):
     def __setattr__(self, key, value):
         self[key] = value
 
+    def __dir__(self):
+                return self.keys()
+
     def __getattr__(self, key):
         try:
             return self[key]

sklearn/datasets/tests/test_base.py

@@ -223,3 +223,9 @@ def test_bunch_pickle_generated_with_0_16_and_read_with_0_17():
     bunch_from_pkl.key = 'changed'
     assert_equal(bunch_from_pkl.key, 'changed')
     assert_equal(bunch_from_pkl['key'], 'changed')
+
+
+def test_bunch_dir():
+    # check that dir (important for autocomplete) shows attributes
+    data = load_iris()
+    assert_true("data" in dir(data))