Make dict key completion more conservative

Only handle subtypes of dict, struct arrays and DataFrames

IPython/core/completer.py

@@ -97,6 +97,21 b" if sys.platform == 'win32':"
 else:
     PROTECTABLES = ' ()[]{}?=\\|;:\'#*"^&'
 
+
+# For dict key completion
+try:
+    import numpy
+except ImportError:
+    STRUCT_ARRAY_TYPES = ()
+else:
+    STRUCT_ARRAY_TYPES = (numpy.ndarray,)
+    try:
+        import pandas
+    except ImportError:
+        KEYED_DICT_TYPES = (dict,)
+    else:
+        KEYED_DICT_TYPES = (dict, pandas.DataFrame)
+
 #-----------------------------------------------------------------------------
 # Main functions and classes
 #-----------------------------------------------------------------------------
@@ -856,14 +871,15 b' class IPCompleter(Completer):'
 
     def dict_key_matches(self, text):
         def get_keys(obj):
-            if not callable(getattr(obj, '__getitem__', None)):
-                return []
-            if hasattr(obj, 'keys'):
+            # Only allow completion for known in-memory dict-like types
+            if isinstance(obj, KEYED_DICT_TYPES):
                 try:
                     return list(obj.keys())
                 except Exception:
                     return []
-            return getattr(getattr(obj, 'dtype', None), 'names', [])
+            elif isinstance(obj, STRUCT_ARRAY_TYPES):
+                return obj.dtype.names or []
+            return []
 
         try:
             regexps = self.__dict_key_regexps

IPython/core/tests/test_completer.py

@@ -584,21 +584,6 b' def test_dict_key_completion_unicode_py3():'
     nt.assert_in(unicode_type(b"a\xd7\x90']", 'utf8'), matches)
 
 
-def test_dict_like_key_completion():
-    """Test dict key completion applies where __getitem__ and keys exist"""
-    class D(object):
-        def __getitem__(self):
-            pass
-        def keys(self):
-            return iter(['hello', 'world'])
-    ip = get_ipython()
-    complete = ip.Completer.complete
-    ip.user_ns['d'] = D()
-    _, matches = complete(line_buffer="d['")
-    nt.assert_in("hello']", matches)
-    nt.assert_in("world']", matches)
-
-
 @dec.skip_without('numpy')
 def test_struct_array_key_completion():
     """Test dict key completion applies to numpy struct arrays"""