From ad6a20267248afcbcd4d4e6c71aa959148ef5507 Mon Sep 17 00:00:00 2001
From: Tom Augspurger <tom.w.augspurger@gmail.com>
Date: Thu, 26 Apr 2018 14:50:32 -0500
Subject: [PATCH 1/7] PERF: Faster Series.__getattribute__

Closes #19764
---
 doc/source/whatsnew/v0.23.0.txt       | 1 +
 pandas/core/generic.py                | 2 +-
 pandas/core/indexes/base.py           | 6 ++++++
 pandas/core/indexes/interval.py       | 1 +
 pandas/core/indexes/numeric.py        | 1 +
 pandas/core/indexes/period.py         | 1 +
 pandas/tests/indexes/datetimelike.py  | 4 ++++
 pandas/tests/indexes/test_base.py     | 4 ++++
 pandas/tests/indexes/test_category.py | 4 ++++
 pandas/tests/indexes/test_multi.py    | 4 ++++
 pandas/tests/indexes/test_numeric.py  | 4 ++++
 pandas/tests/indexes/test_range.py    | 4 ++++
 12 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/doc/source/whatsnew/v0.23.0.txt b/doc/source/whatsnew/v0.23.0.txt
index ffa4f1068f84d..7082850488326 100644
--- a/doc/source/whatsnew/v0.23.0.txt
+++ b/doc/source/whatsnew/v0.23.0.txt
@@ -958,6 +958,7 @@ Performance Improvements
 - Improved performance of :func:`pandas.core.groupby.GroupBy.any` and :func:`pandas.core.groupby.GroupBy.all` (:issue:`15435`)
 - Improved performance of :func:`pandas.core.groupby.GroupBy.pct_change` (:issue:`19165`)
 - Improved performance of :func:`Series.isin` in the case of categorical dtypes (:issue:`20003`)
+- Improved performance of ``Series.__getattribute__`` when the Series has certain index types. This manifiested in slow printing of large Series with a ``DatetimeIndex`` (:issue:`19764`)
 - Fixed a performance regression for :func:`GroupBy.nth` and :func:`GroupBy.last` with some object columns (:issue:`19283`)
 
 .. _whatsnew_0230.docs:
diff --git a/pandas/core/generic.py b/pandas/core/generic.py
index 86342b6996abf..f78b2cb996f42 100644
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -4375,7 +4375,7 @@ def __getattr__(self, name):
                 name in self._accessors):
             return object.__getattribute__(self, name)
         else:
-            if name in self._info_axis:
+            if self._info_axis._is_dotable and name in self._info_axis:
                 return self[name]
             return object.__getattribute__(self, name)
 
diff --git a/pandas/core/indexes/base.py b/pandas/core/indexes/base.py
index 2ceec1592d49b..c87ca9c3c8d04 100644
--- a/pandas/core/indexes/base.py
+++ b/pandas/core/indexes/base.py
@@ -244,6 +244,12 @@ class Index(IndexOpsMixin, PandasObject):
     _engine_type = libindex.ObjectEngine
 
     _accessors = set(['str'])
+    # Whether items can be selected from NDFrame.<item>
+    # Some indexes (DatetimeIndex, Int64Index) cannot contain
+    # valid Python identifiers. Setting _is_dotable = False is an
+    # optimization.
+    # https://github.com/pandas-dev/pandas/issues/19764
+    _is_dotable = True
 
     str = CachedAccessor("str", StringMethods)
 
diff --git a/pandas/core/indexes/interval.py b/pandas/core/indexes/interval.py
index 54800d0d76d2e..82123062cd57a 100644
--- a/pandas/core/indexes/interval.py
+++ b/pandas/core/indexes/interval.py
@@ -207,6 +207,7 @@ class IntervalIndex(IntervalMixin, Index):
     _typ = 'intervalindex'
     _comparables = ['name']
     _attributes = ['name', 'closed']
+    _is_dotable = False  # can't contain Python identifiers
 
     # we would like our indexing holder to defer to us
     _defer_to_indexing = True
diff --git a/pandas/core/indexes/numeric.py b/pandas/core/indexes/numeric.py
index 1fe0c8fa289e6..4267bde342932 100644
--- a/pandas/core/indexes/numeric.py
+++ b/pandas/core/indexes/numeric.py
@@ -31,6 +31,7 @@ class NumericIndex(Index):
 
     """
     _is_numeric_dtype = True
+    _is_dotable = False  # Can't contain Python identifiers
 
     def __new__(cls, data=None, dtype=None, copy=False, name=None,
                 fastpath=False):
diff --git a/pandas/core/indexes/period.py b/pandas/core/indexes/period.py
index 4a224d4e6ee7f..a8ab01c2cb2b0 100644
--- a/pandas/core/indexes/period.py
+++ b/pandas/core/indexes/period.py
@@ -204,6 +204,7 @@ class PeriodIndex(DatelikeOps, DatetimeIndexOpsMixin, Int64Index):
     """
     _typ = 'periodindex'
     _attributes = ['name', 'freq']
+    _is_dotable = False  # Can't contain Python identifiers
 
     # define my properties & methods for delegation
     _other_ops = []
diff --git a/pandas/tests/indexes/datetimelike.py b/pandas/tests/indexes/datetimelike.py
index 7d01a2a70145d..20a03ccaff696 100644
--- a/pandas/tests/indexes/datetimelike.py
+++ b/pandas/tests/indexes/datetimelike.py
@@ -8,6 +8,10 @@
 
 class DatetimeLike(Base):
 
+    def test_is_dotable(self):
+        idx = self.create_index()
+        assert idx._is_dotable is False
+
     def test_shift_identity(self):
 
         idx = self.create_index()
diff --git a/pandas/tests/indexes/test_base.py b/pandas/tests/indexes/test_base.py
index 7cd880b51661d..bda58e9935cc4 100644
--- a/pandas/tests/indexes/test_base.py
+++ b/pandas/tests/indexes/test_base.py
@@ -66,6 +66,10 @@ def generate_index_types(self, skip_index_keys=[]):
             if key not in skip_index_keys:
                 yield key, idx
 
+    def test_is_dotable(self):
+        idx = self.create_index()
+        assert idx._is_dotable is True
+
     def test_new_axis(self):
         new_index = self.dateIndex[None, :]
         assert new_index.ndim == 2
diff --git a/pandas/tests/indexes/test_category.py b/pandas/tests/indexes/test_category.py
index e9fddfde90348..7d72a121d34e0 100644
--- a/pandas/tests/indexes/test_category.py
+++ b/pandas/tests/indexes/test_category.py
@@ -33,6 +33,10 @@ def create_index(self, categories=None, ordered=False):
         return CategoricalIndex(
             list('aabbca'), categories=categories, ordered=ordered)
 
+    def test_is_dotable(self):
+        ci = self.create_index(categories=list('abcd'))
+        assert ci._is_dotable is True
+
     def test_construction(self):
 
         ci = self.create_index(categories=list('abcd'))
diff --git a/pandas/tests/indexes/test_multi.py b/pandas/tests/indexes/test_multi.py
index da11ac645ae07..184aa1f576fbd 100644
--- a/pandas/tests/indexes/test_multi.py
+++ b/pandas/tests/indexes/test_multi.py
@@ -48,6 +48,10 @@ def setup_method(self, method):
     def create_index(self):
         return self.index
 
+    def test_is_dotable(self):
+        idx = self.create_index()
+        assert idx._is_dotable is True
+
     def test_boolean_context_compat2(self):
 
         # boolean context compat
diff --git a/pandas/tests/indexes/test_numeric.py b/pandas/tests/indexes/test_numeric.py
index bafb6ae2e45f4..f09bc1550dca8 100644
--- a/pandas/tests/indexes/test_numeric.py
+++ b/pandas/tests/indexes/test_numeric.py
@@ -64,6 +64,10 @@ def test_index_rdiv_timedelta(self, scalar_td, index):
 
 class Numeric(Base):
 
+    def test_is_dotable(self):
+        idx = self.create_index()
+        assert idx._is_dotable is False
+
     def test_numeric_compat(self):
         pass  # override Base method
 
diff --git a/pandas/tests/indexes/test_range.py b/pandas/tests/indexes/test_range.py
index 8990834ebe91a..a7ec91a6afe13 100644
--- a/pandas/tests/indexes/test_range.py
+++ b/pandas/tests/indexes/test_range.py
@@ -44,6 +44,10 @@ def check_binop(self, ops, scalars, idxs):
                     expected = op(Int64Index(idx), scalar)
                     tm.assert_index_equal(result, expected)
 
+    def test_is_dotable(self):
+        idx = self.create_index()
+        assert idx._is_dotable is False
+
     def test_binops(self):
         ops = [operator.add, operator.sub, operator.mul, operator.floordiv,
                operator.truediv]

From 55072a078bac11ba311ee8f94dd04db384a96f3a Mon Sep 17 00:00:00 2001
From: Tom Augspurger <tom.w.augspurger@gmail.com>
Date: Thu, 26 Apr 2018 15:14:03 -0500
Subject: [PATCH 2/7] Renamed

---
 doc/source/whatsnew/v0.23.0.txt       | 2 +-
 pandas/core/generic.py                | 2 +-
 pandas/core/indexes/base.py           | 4 ++--
 pandas/core/indexes/interval.py       | 2 +-
 pandas/core/indexes/numeric.py        | 2 +-
 pandas/core/indexes/period.py         | 2 +-
 pandas/tests/indexes/datetimelike.py  | 4 ++--
 pandas/tests/indexes/test_base.py     | 4 ++--
 pandas/tests/indexes/test_category.py | 4 ++--
 pandas/tests/indexes/test_multi.py    | 4 ++--
 pandas/tests/indexes/test_numeric.py  | 4 ++--
 pandas/tests/indexes/test_range.py    | 4 ++--
 12 files changed, 19 insertions(+), 19 deletions(-)

diff --git a/doc/source/whatsnew/v0.23.0.txt b/doc/source/whatsnew/v0.23.0.txt
index 7082850488326..c2fdd9bac46e6 100644
--- a/doc/source/whatsnew/v0.23.0.txt
+++ b/doc/source/whatsnew/v0.23.0.txt
@@ -958,7 +958,7 @@ Performance Improvements
 - Improved performance of :func:`pandas.core.groupby.GroupBy.any` and :func:`pandas.core.groupby.GroupBy.all` (:issue:`15435`)
 - Improved performance of :func:`pandas.core.groupby.GroupBy.pct_change` (:issue:`19165`)
 - Improved performance of :func:`Series.isin` in the case of categorical dtypes (:issue:`20003`)
-- Improved performance of ``Series.__getattribute__`` when the Series has certain index types. This manifiested in slow printing of large Series with a ``DatetimeIndex`` (:issue:`19764`)
+- Improved performance of ``getattr(Series, attr)`` when the Series has certain index types. This manifiested in slow printing of large Series with a ``DatetimeIndex`` (:issue:`19764`)
 - Fixed a performance regression for :func:`GroupBy.nth` and :func:`GroupBy.last` with some object columns (:issue:`19283`)
 
 .. _whatsnew_0230.docs:
diff --git a/pandas/core/generic.py b/pandas/core/generic.py
index f78b2cb996f42..588fba69ae497 100644
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -4375,7 +4375,7 @@ def __getattr__(self, name):
                 name in self._accessors):
             return object.__getattribute__(self, name)
         else:
-            if self._info_axis._is_dotable and name in self._info_axis:
+            if self._info_axis.__can_hold_identifiers and name in self._info_axis:
                 return self[name]
             return object.__getattribute__(self, name)
 
diff --git a/pandas/core/indexes/base.py b/pandas/core/indexes/base.py
index c87ca9c3c8d04..4f35e265f2abd 100644
--- a/pandas/core/indexes/base.py
+++ b/pandas/core/indexes/base.py
@@ -246,10 +246,10 @@ class Index(IndexOpsMixin, PandasObject):
     _accessors = set(['str'])
     # Whether items can be selected from NDFrame.<item>
     # Some indexes (DatetimeIndex, Int64Index) cannot contain
-    # valid Python identifiers. Setting _is_dotable = False is an
+    # valid Python identifiers. Setting __can_hold_identifiers = False is an
     # optimization.
     # https://github.com/pandas-dev/pandas/issues/19764
-    _is_dotable = True
+    __can_hold_identifiers = True
 
     str = CachedAccessor("str", StringMethods)
 
diff --git a/pandas/core/indexes/interval.py b/pandas/core/indexes/interval.py
index 82123062cd57a..be9fca9b33c30 100644
--- a/pandas/core/indexes/interval.py
+++ b/pandas/core/indexes/interval.py
@@ -207,7 +207,7 @@ class IntervalIndex(IntervalMixin, Index):
     _typ = 'intervalindex'
     _comparables = ['name']
     _attributes = ['name', 'closed']
-    _is_dotable = False  # can't contain Python identifiers
+    __can_hold_identifiers = False  # can't contain Python identifiers
 
     # we would like our indexing holder to defer to us
     _defer_to_indexing = True
diff --git a/pandas/core/indexes/numeric.py b/pandas/core/indexes/numeric.py
index 4267bde342932..f10c40adf8223 100644
--- a/pandas/core/indexes/numeric.py
+++ b/pandas/core/indexes/numeric.py
@@ -31,7 +31,7 @@ class NumericIndex(Index):
 
     """
     _is_numeric_dtype = True
-    _is_dotable = False  # Can't contain Python identifiers
+    __can_hold_identifiers = False  # Can't contain Python identifiers
 
     def __new__(cls, data=None, dtype=None, copy=False, name=None,
                 fastpath=False):
diff --git a/pandas/core/indexes/period.py b/pandas/core/indexes/period.py
index a8ab01c2cb2b0..867ac136c2bbc 100644
--- a/pandas/core/indexes/period.py
+++ b/pandas/core/indexes/period.py
@@ -204,7 +204,7 @@ class PeriodIndex(DatelikeOps, DatetimeIndexOpsMixin, Int64Index):
     """
     _typ = 'periodindex'
     _attributes = ['name', 'freq']
-    _is_dotable = False  # Can't contain Python identifiers
+    __can_hold_identifiers = False  # Can't contain Python identifiers
 
     # define my properties & methods for delegation
     _other_ops = []
diff --git a/pandas/tests/indexes/datetimelike.py b/pandas/tests/indexes/datetimelike.py
index 20a03ccaff696..ad1ff6380503c 100644
--- a/pandas/tests/indexes/datetimelike.py
+++ b/pandas/tests/indexes/datetimelike.py
@@ -8,9 +8,9 @@
 
 class DatetimeLike(Base):
 
-    def test_is_dotable(self):
+    def test__can_hold_identifiers(self):
         idx = self.create_index()
-        assert idx._is_dotable is False
+        assert idx.__can_hold_identifiers is False
 
     def test_shift_identity(self):
 
diff --git a/pandas/tests/indexes/test_base.py b/pandas/tests/indexes/test_base.py
index bda58e9935cc4..303b13f1796db 100644
--- a/pandas/tests/indexes/test_base.py
+++ b/pandas/tests/indexes/test_base.py
@@ -66,9 +66,9 @@ def generate_index_types(self, skip_index_keys=[]):
             if key not in skip_index_keys:
                 yield key, idx
 
-    def test_is_dotable(self):
+    def test__can_hold_identifiers(self):
         idx = self.create_index()
-        assert idx._is_dotable is True
+        assert idx.__can_hold_identifiers is True
 
     def test_new_axis(self):
         new_index = self.dateIndex[None, :]
diff --git a/pandas/tests/indexes/test_category.py b/pandas/tests/indexes/test_category.py
index 7d72a121d34e0..324c8d63d45ec 100644
--- a/pandas/tests/indexes/test_category.py
+++ b/pandas/tests/indexes/test_category.py
@@ -33,9 +33,9 @@ def create_index(self, categories=None, ordered=False):
         return CategoricalIndex(
             list('aabbca'), categories=categories, ordered=ordered)
 
-    def test_is_dotable(self):
+    def test__can_hold_identifiers(self):
         ci = self.create_index(categories=list('abcd'))
-        assert ci._is_dotable is True
+        assert ci.__can_hold_identifiers is True
 
     def test_construction(self):
 
diff --git a/pandas/tests/indexes/test_multi.py b/pandas/tests/indexes/test_multi.py
index 184aa1f576fbd..a2b4dcc7aba95 100644
--- a/pandas/tests/indexes/test_multi.py
+++ b/pandas/tests/indexes/test_multi.py
@@ -48,9 +48,9 @@ def setup_method(self, method):
     def create_index(self):
         return self.index
 
-    def test_is_dotable(self):
+    def test__can_hold_identifiers(self):
         idx = self.create_index()
-        assert idx._is_dotable is True
+        assert idx.__can_hold_identifiers is True
 
     def test_boolean_context_compat2(self):
 
diff --git a/pandas/tests/indexes/test_numeric.py b/pandas/tests/indexes/test_numeric.py
index f09bc1550dca8..dc687e623893f 100644
--- a/pandas/tests/indexes/test_numeric.py
+++ b/pandas/tests/indexes/test_numeric.py
@@ -64,9 +64,9 @@ def test_index_rdiv_timedelta(self, scalar_td, index):
 
 class Numeric(Base):
 
-    def test_is_dotable(self):
+    def test__can_hold_identifiers(self):
         idx = self.create_index()
-        assert idx._is_dotable is False
+        assert idx.__can_hold_identifiers is False
 
     def test_numeric_compat(self):
         pass  # override Base method
diff --git a/pandas/tests/indexes/test_range.py b/pandas/tests/indexes/test_range.py
index a7ec91a6afe13..75722bfde70df 100644
--- a/pandas/tests/indexes/test_range.py
+++ b/pandas/tests/indexes/test_range.py
@@ -44,9 +44,9 @@ def check_binop(self, ops, scalars, idxs):
                     expected = op(Int64Index(idx), scalar)
                     tm.assert_index_equal(result, expected)
 
-    def test_is_dotable(self):
+    def test__can_hold_identifiers(self):
         idx = self.create_index()
-        assert idx._is_dotable is False
+        assert idx.__can_hold_identifiers is False
 
     def test_binops(self):
         ops = [operator.add, operator.sub, operator.mul, operator.floordiv,

From ad871ce05b0d36f77582bb10fe62c100711f327e Mon Sep 17 00:00:00 2001
From: Tom Augspurger <tom.w.augspurger@gmail.com>
Date: Thu, 26 Apr 2018 15:16:51 -0500
Subject: [PATCH 3/7] Linting

---
 pandas/core/generic.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/pandas/core/generic.py b/pandas/core/generic.py
index 588fba69ae497..4b7225dd9a60b 100644
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -4375,7 +4375,8 @@ def __getattr__(self, name):
                 name in self._accessors):
             return object.__getattribute__(self, name)
         else:
-            if self._info_axis.__can_hold_identifiers and name in self._info_axis:
+            if (self._info_axis.__can_hold_identifiers and
+                    name in self._info_axis):
                 return self[name]
             return object.__getattribute__(self, name)
 

From 4b7334c577f39aaecbb0285df4d32a1b7129c428 Mon Sep 17 00:00:00 2001
From: Tom Augspurger <tom.w.augspurger@gmail.com>
Date: Thu, 26 Apr 2018 16:40:05 -0500
Subject: [PATCH 4/7] Fixed find-replace fail

---
 pandas/core/generic.py                | 2 +-
 pandas/core/indexes/base.py           | 4 ++--
 pandas/core/indexes/interval.py       | 2 +-
 pandas/core/indexes/numeric.py        | 2 +-
 pandas/core/indexes/period.py         | 2 +-
 pandas/tests/indexes/datetimelike.py  | 4 ++--
 pandas/tests/indexes/test_base.py     | 4 ++--
 pandas/tests/indexes/test_category.py | 4 ++--
 pandas/tests/indexes/test_multi.py    | 4 ++--
 pandas/tests/indexes/test_numeric.py  | 4 ++--
 pandas/tests/indexes/test_range.py    | 4 ++--
 11 files changed, 18 insertions(+), 18 deletions(-)

diff --git a/pandas/core/generic.py b/pandas/core/generic.py
index 4b7225dd9a60b..e7de5b502750c 100644
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -4375,7 +4375,7 @@ def __getattr__(self, name):
                 name in self._accessors):
             return object.__getattribute__(self, name)
         else:
-            if (self._info_axis.__can_hold_identifiers and
+            if (self._info_axis._can_hold_identifiers and
                     name in self._info_axis):
                 return self[name]
             return object.__getattribute__(self, name)
diff --git a/pandas/core/indexes/base.py b/pandas/core/indexes/base.py
index 4f35e265f2abd..b596698d844fa 100644
--- a/pandas/core/indexes/base.py
+++ b/pandas/core/indexes/base.py
@@ -246,10 +246,10 @@ class Index(IndexOpsMixin, PandasObject):
     _accessors = set(['str'])
     # Whether items can be selected from NDFrame.<item>
     # Some indexes (DatetimeIndex, Int64Index) cannot contain
-    # valid Python identifiers. Setting __can_hold_identifiers = False is an
+    # valid Python identifiers. Setting _can_hold_identifiers = False is an
     # optimization.
     # https://github.com/pandas-dev/pandas/issues/19764
-    __can_hold_identifiers = True
+    _can_hold_identifiers = True
 
     str = CachedAccessor("str", StringMethods)
 
diff --git a/pandas/core/indexes/interval.py b/pandas/core/indexes/interval.py
index be9fca9b33c30..515f15e7c691a 100644
--- a/pandas/core/indexes/interval.py
+++ b/pandas/core/indexes/interval.py
@@ -207,7 +207,7 @@ class IntervalIndex(IntervalMixin, Index):
     _typ = 'intervalindex'
     _comparables = ['name']
     _attributes = ['name', 'closed']
-    __can_hold_identifiers = False  # can't contain Python identifiers
+    _can_hold_identifiers = False  # can't contain Python identifiers
 
     # we would like our indexing holder to defer to us
     _defer_to_indexing = True
diff --git a/pandas/core/indexes/numeric.py b/pandas/core/indexes/numeric.py
index f10c40adf8223..c50bc09b45904 100644
--- a/pandas/core/indexes/numeric.py
+++ b/pandas/core/indexes/numeric.py
@@ -31,7 +31,7 @@ class NumericIndex(Index):
 
     """
     _is_numeric_dtype = True
-    __can_hold_identifiers = False  # Can't contain Python identifiers
+    _can_hold_identifiers = False  # Can't contain Python identifiers
 
     def __new__(cls, data=None, dtype=None, copy=False, name=None,
                 fastpath=False):
diff --git a/pandas/core/indexes/period.py b/pandas/core/indexes/period.py
index 867ac136c2bbc..5558616c93998 100644
--- a/pandas/core/indexes/period.py
+++ b/pandas/core/indexes/period.py
@@ -204,7 +204,7 @@ class PeriodIndex(DatelikeOps, DatetimeIndexOpsMixin, Int64Index):
     """
     _typ = 'periodindex'
     _attributes = ['name', 'freq']
-    __can_hold_identifiers = False  # Can't contain Python identifiers
+    _can_hold_identifiers = False  # Can't contain Python identifiers
 
     # define my properties & methods for delegation
     _other_ops = []
diff --git a/pandas/tests/indexes/datetimelike.py b/pandas/tests/indexes/datetimelike.py
index ad1ff6380503c..7b16877abe91f 100644
--- a/pandas/tests/indexes/datetimelike.py
+++ b/pandas/tests/indexes/datetimelike.py
@@ -8,9 +8,9 @@
 
 class DatetimeLike(Base):
 
-    def test__can_hold_identifiers(self):
+    def test_can_hold_identifiers(self):
         idx = self.create_index()
-        assert idx.__can_hold_identifiers is False
+        assert idx._can_hold_identifiers is False
 
     def test_shift_identity(self):
 
diff --git a/pandas/tests/indexes/test_base.py b/pandas/tests/indexes/test_base.py
index 303b13f1796db..bc61a87048da0 100644
--- a/pandas/tests/indexes/test_base.py
+++ b/pandas/tests/indexes/test_base.py
@@ -66,9 +66,9 @@ def generate_index_types(self, skip_index_keys=[]):
             if key not in skip_index_keys:
                 yield key, idx
 
-    def test__can_hold_identifiers(self):
+    def test_can_hold_identifiers(self):
         idx = self.create_index()
-        assert idx.__can_hold_identifiers is True
+        assert idx._can_hold_identifiers is True
 
     def test_new_axis(self):
         new_index = self.dateIndex[None, :]
diff --git a/pandas/tests/indexes/test_category.py b/pandas/tests/indexes/test_category.py
index 324c8d63d45ec..401d9e5490f76 100644
--- a/pandas/tests/indexes/test_category.py
+++ b/pandas/tests/indexes/test_category.py
@@ -33,9 +33,9 @@ def create_index(self, categories=None, ordered=False):
         return CategoricalIndex(
             list('aabbca'), categories=categories, ordered=ordered)
 
-    def test__can_hold_identifiers(self):
+    def test_can_hold_identifiers(self):
         ci = self.create_index(categories=list('abcd'))
-        assert ci.__can_hold_identifiers is True
+        assert ci._can_hold_identifiers is True
 
     def test_construction(self):
 
diff --git a/pandas/tests/indexes/test_multi.py b/pandas/tests/indexes/test_multi.py
index a2b4dcc7aba95..fde2ef47087fa 100644
--- a/pandas/tests/indexes/test_multi.py
+++ b/pandas/tests/indexes/test_multi.py
@@ -48,9 +48,9 @@ def setup_method(self, method):
     def create_index(self):
         return self.index
 
-    def test__can_hold_identifiers(self):
+    def test_can_hold_identifiers(self):
         idx = self.create_index()
-        assert idx.__can_hold_identifiers is True
+        assert idx._can_hold_identifiers is True
 
     def test_boolean_context_compat2(self):
 
diff --git a/pandas/tests/indexes/test_numeric.py b/pandas/tests/indexes/test_numeric.py
index dc687e623893f..d94c1f2889894 100644
--- a/pandas/tests/indexes/test_numeric.py
+++ b/pandas/tests/indexes/test_numeric.py
@@ -64,9 +64,9 @@ def test_index_rdiv_timedelta(self, scalar_td, index):
 
 class Numeric(Base):
 
-    def test__can_hold_identifiers(self):
+    def test_can_hold_identifiers(self):
         idx = self.create_index()
-        assert idx.__can_hold_identifiers is False
+        assert idx._can_hold_identifiers is False
 
     def test_numeric_compat(self):
         pass  # override Base method
diff --git a/pandas/tests/indexes/test_range.py b/pandas/tests/indexes/test_range.py
index 75722bfde70df..732e4947f65c2 100644
--- a/pandas/tests/indexes/test_range.py
+++ b/pandas/tests/indexes/test_range.py
@@ -44,9 +44,9 @@ def check_binop(self, ops, scalars, idxs):
                     expected = op(Int64Index(idx), scalar)
                     tm.assert_index_equal(result, expected)
 
-    def test__can_hold_identifiers(self):
+    def test_can_hold_identifiers(self):
         idx = self.create_index()
-        assert idx.__can_hold_identifiers is False
+        assert idx._can_hold_identifiers is False
 
     def test_binops(self):
         ops = [operator.add, operator.sub, operator.mul, operator.floordiv,

From 857364f4112749a8f7e3131dc58b05e73d377e67 Mon Sep 17 00:00:00 2001
From: Tom Augspurger <tom.w.augspurger@gmail.com>
Date: Sat, 28 Apr 2018 11:46:18 -0500
Subject: [PATCH 5/7] asv

---
 asv_bench/benchmarks/series_methods.py | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/asv_bench/benchmarks/series_methods.py b/asv_bench/benchmarks/series_methods.py
index 478aba278029c..3f6522c3403d9 100644
--- a/asv_bench/benchmarks/series_methods.py
+++ b/asv_bench/benchmarks/series_methods.py
@@ -121,3 +121,16 @@ def setup(self):
 
     def time_dir_strings(self):
         dir(self.s)
+
+
+class SeriesGetattr(object):
+    # https://github.com/pandas-dev/pandas/issues/19764
+    goal_time = 0.2
+
+    def setup(self):
+        self.s = Series(1,
+                        index=date_range("2012-01-01", freq='s',
+                                         periods=int(1e6)))
+
+    def time_series_datetimeindex_repr(self):
+        getattr(self.s, 'a', None)

From e0710f304c53b0b2f027dc2cdec37a20084bed16 Mon Sep 17 00:00:00 2001
From: Tom Augspurger <tom.w.augspurger@gmail.com>
Date: Mon, 30 Apr 2018 06:03:35 -0500
Subject: [PATCH 6/7] Move to instance properties

---
 pandas/core/indexes/base.py     | 23 +++++++++++++++++------
 pandas/core/indexes/interval.py |  7 ++++++-
 pandas/core/indexes/numeric.py  |  7 ++++++-
 pandas/core/indexes/period.py   |  1 -
 4 files changed, 29 insertions(+), 9 deletions(-)

diff --git a/pandas/core/indexes/base.py b/pandas/core/indexes/base.py
index b596698d844fa..3381755f753b1 100644
--- a/pandas/core/indexes/base.py
+++ b/pandas/core/indexes/base.py
@@ -244,12 +244,6 @@ class Index(IndexOpsMixin, PandasObject):
     _engine_type = libindex.ObjectEngine
 
     _accessors = set(['str'])
-    # Whether items can be selected from NDFrame.<item>
-    # Some indexes (DatetimeIndex, Int64Index) cannot contain
-    # valid Python identifiers. Setting _can_hold_identifiers = False is an
-    # optimization.
-    # https://github.com/pandas-dev/pandas/issues/19764
-    _can_hold_identifiers = True
 
     str = CachedAccessor("str", StringMethods)
 
@@ -2089,6 +2083,23 @@ def __getitem__(self, key):
         else:
             return result
 
+    @property
+    def _can_hold_identifiers(self):
+        """
+        Whether the Index class *can* hold Python identifiers.
+
+        This is useful for short-circuting lookups in NDFrame.__getattr__.
+        Some index-classes can't hold identifiers (NumericIndex,
+        DatetimeIndex), so there's no reason to search the index when a user
+        does `Series.foo<TAB>`.
+
+        Note that we don't care about `foo` here. This just a property
+        of the index class itself, nothing to do with an instance.
+
+        https://github.com/pandas-dev/pandas/issues/19764
+        """
+        return True
+
     def append(self, other):
         """
         Append a collection of Index options together
diff --git a/pandas/core/indexes/interval.py b/pandas/core/indexes/interval.py
index 515f15e7c691a..cbc8ebe5ce2b2 100644
--- a/pandas/core/indexes/interval.py
+++ b/pandas/core/indexes/interval.py
@@ -207,7 +207,6 @@ class IntervalIndex(IntervalMixin, Index):
     _typ = 'intervalindex'
     _comparables = ['name']
     _attributes = ['name', 'closed']
-    _can_hold_identifiers = False  # can't contain Python identifiers
 
     # we would like our indexing holder to defer to us
     _defer_to_indexing = True
@@ -1304,6 +1303,12 @@ def __getitem__(self, value):
 
         return self._shallow_copy(left, right)
 
+    @property
+    def _can_hold_identifiers(self):
+        # perf: Intervals aren't valid Python identifiers.
+        # https://github.com/pandas-dev/pandas/issues/19764
+        return False
+
     # __repr__ associated methods are based on MultiIndex
 
     def _format_with_header(self, header, **kwargs):
diff --git a/pandas/core/indexes/numeric.py b/pandas/core/indexes/numeric.py
index c50bc09b45904..dbb982318e4b0 100644
--- a/pandas/core/indexes/numeric.py
+++ b/pandas/core/indexes/numeric.py
@@ -31,7 +31,6 @@ class NumericIndex(Index):
 
     """
     _is_numeric_dtype = True
-    _can_hold_identifiers = False  # Can't contain Python identifiers
 
     def __new__(cls, data=None, dtype=None, copy=False, name=None,
                 fastpath=False):
@@ -115,6 +114,12 @@ def is_all_dates(self):
         """
         return False
 
+    @property
+    def _can_hold_identifiers(self):
+        # perf: Numeric elements are not valid identifiers.
+        # https://github.com/pandas-dev/pandas/issues/19764
+        return False
+
 
 _num_index_shared_docs['class_descr'] = """
     Immutable ndarray implementing an ordered, sliceable set. The basic object
diff --git a/pandas/core/indexes/period.py b/pandas/core/indexes/period.py
index 5558616c93998..4a224d4e6ee7f 100644
--- a/pandas/core/indexes/period.py
+++ b/pandas/core/indexes/period.py
@@ -204,7 +204,6 @@ class PeriodIndex(DatelikeOps, DatetimeIndexOpsMixin, Int64Index):
     """
     _typ = 'periodindex'
     _attributes = ['name', 'freq']
-    _can_hold_identifiers = False  # Can't contain Python identifiers
 
     # define my properties & methods for delegation
     _other_ops = []

From 1b598d0b99b7804f8c0c8cef21393bd7959764f4 Mon Sep 17 00:00:00 2001
From: Tom Augspurger <tom.w.augspurger@gmail.com>
Date: Mon, 30 Apr 2018 19:10:03 -0500
Subject: [PATCH 7/7] function

---
 pandas/core/generic.py                |  3 +--
 pandas/core/indexes/base.py           | 20 ++++++++------------
 pandas/core/indexes/interval.py       |  6 ------
 pandas/core/indexes/numeric.py        |  6 ------
 pandas/tests/indexes/datetimelike.py  |  3 ++-
 pandas/tests/indexes/test_base.py     |  3 ++-
 pandas/tests/indexes/test_category.py |  5 +++--
 pandas/tests/indexes/test_multi.py    |  3 ++-
 pandas/tests/indexes/test_numeric.py  |  3 ++-
 pandas/tests/indexes/test_range.py    |  3 ++-
 10 files changed, 22 insertions(+), 33 deletions(-)

diff --git a/pandas/core/generic.py b/pandas/core/generic.py
index e7de5b502750c..75216f12e5739 100644
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -4375,8 +4375,7 @@ def __getattr__(self, name):
                 name in self._accessors):
             return object.__getattribute__(self, name)
         else:
-            if (self._info_axis._can_hold_identifiers and
-                    name in self._info_axis):
+            if self._info_axis._can_hold_identifiers_and_holds_name(name):
                 return self[name]
             return object.__getattribute__(self, name)
 
diff --git a/pandas/core/indexes/base.py b/pandas/core/indexes/base.py
index 3381755f753b1..f208687a0cf1b 100644
--- a/pandas/core/indexes/base.py
+++ b/pandas/core/indexes/base.py
@@ -2083,22 +2083,18 @@ def __getitem__(self, key):
         else:
             return result
 
-    @property
-    def _can_hold_identifiers(self):
+    def _can_hold_identifiers_and_holds_name(self, name):
         """
-        Whether the Index class *can* hold Python identifiers.
-
-        This is useful for short-circuting lookups in NDFrame.__getattr__.
-        Some index-classes can't hold identifiers (NumericIndex,
-        DatetimeIndex), so there's no reason to search the index when a user
-        does `Series.foo<TAB>`.
-
-        Note that we don't care about `foo` here. This just a property
-        of the index class itself, nothing to do with an instance.
+        Faster check for ``name in self`` when we know `name` is a Python
+        identifier (e.g. in NDFrame.__getattr__, which hits this to support
+        . key lookup). For indexes that can't hold identifiers (everything
+        but object & categorical) we just return False.
 
         https://github.com/pandas-dev/pandas/issues/19764
         """
-        return True
+        if self.is_object() or self.is_categorical():
+            return name in self
+        return False
 
     def append(self, other):
         """
diff --git a/pandas/core/indexes/interval.py b/pandas/core/indexes/interval.py
index cbc8ebe5ce2b2..54800d0d76d2e 100644
--- a/pandas/core/indexes/interval.py
+++ b/pandas/core/indexes/interval.py
@@ -1303,12 +1303,6 @@ def __getitem__(self, value):
 
         return self._shallow_copy(left, right)
 
-    @property
-    def _can_hold_identifiers(self):
-        # perf: Intervals aren't valid Python identifiers.
-        # https://github.com/pandas-dev/pandas/issues/19764
-        return False
-
     # __repr__ associated methods are based on MultiIndex
 
     def _format_with_header(self, header, **kwargs):
diff --git a/pandas/core/indexes/numeric.py b/pandas/core/indexes/numeric.py
index dbb982318e4b0..1fe0c8fa289e6 100644
--- a/pandas/core/indexes/numeric.py
+++ b/pandas/core/indexes/numeric.py
@@ -114,12 +114,6 @@ def is_all_dates(self):
         """
         return False
 
-    @property
-    def _can_hold_identifiers(self):
-        # perf: Numeric elements are not valid identifiers.
-        # https://github.com/pandas-dev/pandas/issues/19764
-        return False
-
 
 _num_index_shared_docs['class_descr'] = """
     Immutable ndarray implementing an ordered, sliceable set. The basic object
diff --git a/pandas/tests/indexes/datetimelike.py b/pandas/tests/indexes/datetimelike.py
index 7b16877abe91f..e32e18ea0ec4a 100644
--- a/pandas/tests/indexes/datetimelike.py
+++ b/pandas/tests/indexes/datetimelike.py
@@ -10,7 +10,8 @@ class DatetimeLike(Base):
 
     def test_can_hold_identifiers(self):
         idx = self.create_index()
-        assert idx._can_hold_identifiers is False
+        key = idx[0]
+        assert idx._can_hold_identifiers_and_holds_name(key) is False
 
     def test_shift_identity(self):
 
diff --git a/pandas/tests/indexes/test_base.py b/pandas/tests/indexes/test_base.py
index bc61a87048da0..95ddf1f6cd8bd 100644
--- a/pandas/tests/indexes/test_base.py
+++ b/pandas/tests/indexes/test_base.py
@@ -68,7 +68,8 @@ def generate_index_types(self, skip_index_keys=[]):
 
     def test_can_hold_identifiers(self):
         idx = self.create_index()
-        assert idx._can_hold_identifiers is True
+        key = idx[0]
+        assert idx._can_hold_identifiers_and_holds_name(key) is True
 
     def test_new_axis(self):
         new_index = self.dateIndex[None, :]
diff --git a/pandas/tests/indexes/test_category.py b/pandas/tests/indexes/test_category.py
index 401d9e5490f76..6a1a1a5bdba4f 100644
--- a/pandas/tests/indexes/test_category.py
+++ b/pandas/tests/indexes/test_category.py
@@ -34,8 +34,9 @@ def create_index(self, categories=None, ordered=False):
             list('aabbca'), categories=categories, ordered=ordered)
 
     def test_can_hold_identifiers(self):
-        ci = self.create_index(categories=list('abcd'))
-        assert ci._can_hold_identifiers is True
+        idx = self.create_index(categories=list('abcd'))
+        key = idx[0]
+        assert idx._can_hold_identifiers_and_holds_name(key) is True
 
     def test_construction(self):
 
diff --git a/pandas/tests/indexes/test_multi.py b/pandas/tests/indexes/test_multi.py
index fde2ef47087fa..37f70090c179f 100644
--- a/pandas/tests/indexes/test_multi.py
+++ b/pandas/tests/indexes/test_multi.py
@@ -50,7 +50,8 @@ def create_index(self):
 
     def test_can_hold_identifiers(self):
         idx = self.create_index()
-        assert idx._can_hold_identifiers is True
+        key = idx[0]
+        assert idx._can_hold_identifiers_and_holds_name(key) is True
 
     def test_boolean_context_compat2(self):
 
diff --git a/pandas/tests/indexes/test_numeric.py b/pandas/tests/indexes/test_numeric.py
index d94c1f2889894..49322d9b7abd6 100644
--- a/pandas/tests/indexes/test_numeric.py
+++ b/pandas/tests/indexes/test_numeric.py
@@ -66,7 +66,8 @@ class Numeric(Base):
 
     def test_can_hold_identifiers(self):
         idx = self.create_index()
-        assert idx._can_hold_identifiers is False
+        key = idx[0]
+        assert idx._can_hold_identifiers_and_holds_name(key) is False
 
     def test_numeric_compat(self):
         pass  # override Base method
diff --git a/pandas/tests/indexes/test_range.py b/pandas/tests/indexes/test_range.py
index 732e4947f65c2..38f4b341116b8 100644
--- a/pandas/tests/indexes/test_range.py
+++ b/pandas/tests/indexes/test_range.py
@@ -46,7 +46,8 @@ def check_binop(self, ops, scalars, idxs):
 
     def test_can_hold_identifiers(self):
         idx = self.create_index()
-        assert idx._can_hold_identifiers is False
+        key = idx[0]
+        assert idx._can_hold_identifiers_and_holds_name(key) is False
 
     def test_binops(self):
         ops = [operator.add, operator.sub, operator.mul, operator.floordiv,