PERF: faster dir() calls

doc/source/whatsnew/v1.2.0.rst

@@ -346,6 +346,7 @@ Performance improvements
 - Performance improvement in :meth:`RollingGroupby.count` (:issue:`35625`)
 - Small performance decrease to :meth:`Rolling.min` and :meth:`Rolling.max` for fixed windows (:issue:`36567`)
 - Reduced peak memory usage in :meth:`DataFrame.to_pickle` when using ``protocol=5`` in python 3.8+ (:issue:`34244`)
+- faster ``dir`` calls when many index labels, e.g. ``dir(ser)`` (:issue:`37450`)
 - Performance improvement in :class:`ExpandingGroupby` (:issue:`37064`)
 
 .. ---------------------------------------------------------------------------

pandas/core/accessor.py

@@ -24,14 +24,7 @@ def _dir_additions(self) -> Set[str]:
         """
         Add additional __dir__ for this object.
         """
-        rv = set()
-        for accessor in self._accessors:
-            try:
-                getattr(self, accessor)
-                rv.add(accessor)
-            except AttributeError:
-                pass
-        return rv
+        return {accessor for accessor in self._accessors if hasattr(self, accessor)}
 
     def __dir__(self) -> List[str]:
         """

pandas/core/generic.py

@@ -5439,11 +5439,7 @@ def _dir_additions(self) -> Set[str]:
         add the string-like attributes from the info_axis.
         If info_axis is a MultiIndex, it's first level values are used.
         """
-        additions = {
-            c
-            for c in self._info_axis.unique(level=0)[:100]
-            if isinstance(c, str) and c.isidentifier()
-        }
+        additions = self._info_axis._dir_additions_for_owner
         return super()._dir_additions().union(additions)
 
     # ----------------------------------------------------------------------

pandas/core/indexes/base.py

@@ -12,6 +12,7 @@
     NewType,
     Optional,
     Sequence,
+    Set,
     Tuple,
     TypeVar,
     Union,
@@ -568,6 +569,18 @@ def _engine(self):
         target_values = self._get_engine_target()
         return self._engine_type(lambda: target_values, len(self))
 
+    @cache_readonly
+    def _dir_additions_for_owner(self) -> Set[str_t]:
+        """
+        Add the string-like attributes from this index to the owners' dir output.
+        If this is a MultiIndex, it's first level values are used.
+        """
+        return {
+            c
+            for c in self.unique(level=0)[:100]
+            if isinstance(c, str) and c.isidentifier()
+        }
+
     # --------------------------------------------------------------------
     # Array-Like Methods
 

pandas/core/indexes/datetimelike.py

@@ -2,7 +2,7 @@
 Base and utility classes for tseries type pandas objects.
 """
 from datetime import datetime, tzinfo
-from typing import TYPE_CHECKING, Any, List, Optional, TypeVar, Union, cast
+from typing import TYPE_CHECKING, Any, List, Optional, Set, TypeVar, Union, cast
 
 import numpy as np
 
@@ -105,6 +105,10 @@ class DatetimeIndexOpsMixin(ExtensionIndex):
     def _is_all_dates(self) -> bool:
         return True
 
+    @cache_readonly
+    def _dir_additions_for_owner(self) -> Set[str]:
+        return set()
+
     # ------------------------------------------------------------------------
     # Abstract data attributes
 

pandas/core/indexes/interval.py

@@ -2,7 +2,7 @@
 from functools import wraps
 from operator import le, lt
 import textwrap
-from typing import TYPE_CHECKING, Any, List, Optional, Tuple, Union, cast
+from typing import TYPE_CHECKING, Any, List, Optional, Set, Tuple, Union, cast
 
 import numpy as np
 
@@ -371,6 +371,10 @@ def __contains__(self, key: Any) -> bool:
     def _multiindex(self) -> MultiIndex:
         return MultiIndex.from_arrays([self.left, self.right], names=["left", "right"])
 
+    @cache_readonly
+    def _dir_additions_for_owner(self) -> Set[str]:
+        return set()
+
     @cache_readonly
     def values(self) -> IntervalArray:
         """

pandas/core/indexes/numeric.py

@@ -1,4 +1,4 @@
-from typing import Any
+from typing import Any, Set
 
 import numpy as np
 
@@ -184,6 +184,10 @@ def _union(self, other, sort):
         else:
             return super()._union(other, sort)
 
+    @cache_readonly
+    def _dir_additions_for_owner(self) -> Set[str]:
+        return set()
+
 
 _num_index_shared_docs[
     "class_descr"