From d3b361cd0b1cdc7dfbc6c1f71e7b148fa1f2098e Mon Sep 17 00:00:00 2001
From: jbrockmendel <jbrockmendel@gmail.com>
Date: Mon, 3 Feb 2020 16:08:14 -0800
Subject: [PATCH 1/5] REF: call _maybe_cast_integer first

---
 pandas/core/indexes/base.py                 |  4 +--
 pandas/core/indexes/category.py             | 38 ++-------------------
 pandas/tests/indexes/multi/test_indexing.py |  2 +-
 pandas/tests/indexes/test_numeric.py        |  2 +-
 pandas/tests/indexing/test_floats.py        | 12 +++----
 5 files changed, 12 insertions(+), 46 deletions(-)

diff --git a/pandas/core/indexes/base.py b/pandas/core/indexes/base.py
index 6a7551391f2a8..7fdf137416774 100644
--- a/pandas/core/indexes/base.py
+++ b/pandas/core/indexes/base.py
@@ -2889,9 +2889,9 @@ def get_loc(self, key, method=None, tolerance=None):
                     "backfill or nearest lookups"
                 )
             try:
-                return self._engine.get_loc(key)
-            except KeyError:
                 return self._engine.get_loc(self._maybe_cast_indexer(key))
+            except KeyError:
+                raise KeyError(key)
 
         if tolerance is not None:
             tolerance = self._convert_tolerance(tolerance, np.asarray(key))
diff --git a/pandas/core/indexes/category.py b/pandas/core/indexes/category.py
index 2cdf47ad61cec..e87275a5a20f3 100644
--- a/pandas/core/indexes/category.py
+++ b/pandas/core/indexes/category.py
@@ -450,44 +450,10 @@ def _to_safe_for_reshape(self):
         """ convert to object if we are a categorical """
         return self.astype("object")
 
-    def get_loc(self, key, method=None):
-        """
-        Get integer location, slice or boolean mask for requested label.
-
-        Parameters
-        ----------
-        key : label
-        method : {None}
-            * default: exact matches only.
-
-        Returns
-        -------
-        loc : int if unique index, slice if monotonic index, else mask
-
-        Raises
-        ------
-        KeyError : if the key is not in the index
-
-        Examples
-        --------
-        >>> unique_index = pd.CategoricalIndex(list('abc'))
-        >>> unique_index.get_loc('b')
-        1
-
-        >>> monotonic_index = pd.CategoricalIndex(list('abbc'))
-        >>> monotonic_index.get_loc('b')
-        slice(1, 3, None)
-
-        >>> non_monotonic_index = pd.CategoricalIndex(list('abcb'))
-        >>> non_monotonic_index.get_loc('b')
-        array([False,  True, False,  True], dtype=bool)
-        """
+    def _maybe_cast_indexer(self, key):
         code = self.categories.get_loc(key)
         code = self.codes.dtype.type(code)
-        try:
-            return self._engine.get_loc(code)
-        except KeyError:
-            raise KeyError(key)
+        return code
 
     def get_value(self, series: "Series", key: Any):
         """
diff --git a/pandas/tests/indexes/multi/test_indexing.py b/pandas/tests/indexes/multi/test_indexing.py
index b08280a712642..21a4773fa3683 100644
--- a/pandas/tests/indexes/multi/test_indexing.py
+++ b/pandas/tests/indexes/multi/test_indexing.py
@@ -392,7 +392,7 @@ def test_get_loc_missing_nan():
     # GH 8569
     idx = MultiIndex.from_arrays([[1.0, 2.0], [3.0, 4.0]])
     assert isinstance(idx.get_loc(1), slice)
-    with pytest.raises(KeyError, match=r"^3\.0$"):
+    with pytest.raises(KeyError, match=r"^3$"):
         idx.get_loc(3)
     with pytest.raises(KeyError, match=r"^nan$"):
         idx.get_loc(np.nan)
diff --git a/pandas/tests/indexes/test_numeric.py b/pandas/tests/indexes/test_numeric.py
index 992a91ad8a528..1b504ce99604d 100644
--- a/pandas/tests/indexes/test_numeric.py
+++ b/pandas/tests/indexes/test_numeric.py
@@ -385,7 +385,7 @@ def test_get_loc_missing_nan(self):
         # GH 8569
         idx = Float64Index([1, 2])
         assert idx.get_loc(1) == 0
-        with pytest.raises(KeyError, match=r"^3\.0$"):
+        with pytest.raises(KeyError, match=r"^3$"):
             idx.get_loc(3)
         with pytest.raises(KeyError, match="^nan$"):
             idx.get_loc(np.nan)
diff --git a/pandas/tests/indexing/test_floats.py b/pandas/tests/indexing/test_floats.py
index 5530896a90941..89647e87445fc 100644
--- a/pandas/tests/indexing/test_floats.py
+++ b/pandas/tests/indexing/test_floats.py
@@ -107,7 +107,7 @@ def test_scalar_non_numeric(self):
                     "mixed",
                 }:
                     error = KeyError
-                    msg = r"^3$"
+                    msg = r"^3\.0$"
                 else:
                     error = TypeError
                     msg = (
@@ -187,7 +187,7 @@ def test_scalar_with_mixed(self):
             with pytest.raises(TypeError, match=msg):
                 idxr(s2)[1.0]
 
-        with pytest.raises(KeyError, match=r"^1$"):
+        with pytest.raises(KeyError, match=r"^1\.0$"):
             s2.loc[1.0]
 
         result = s2.loc["b"]
@@ -213,7 +213,7 @@ def test_scalar_with_mixed(self):
         msg = "Cannot index by location index with a non-integer key"
         with pytest.raises(TypeError, match=msg):
             s3.iloc[1.0]
-        with pytest.raises(KeyError, match=r"^1$"):
+        with pytest.raises(KeyError, match=r"^1\.0$"):
             s3.loc[1.0]
 
         result = s3.loc[1.5]
@@ -666,11 +666,11 @@ def test_floating_misc(self):
         # value not found (and no fallbacking at all)
 
         # scalar integers
-        with pytest.raises(KeyError, match=r"^4\.0$"):
+        with pytest.raises(KeyError, match=r"^4$"):
             s.loc[4]
-        with pytest.raises(KeyError, match=r"^4\.0$"):
+        with pytest.raises(KeyError, match=r"^4$"):
             s.loc[4]
-        with pytest.raises(KeyError, match=r"^4\.0$"):
+        with pytest.raises(KeyError, match=r"^4$"):
             s[4]
 
         # fancy floats/integers create the correct entry (as nan)

From 3ba28331848c120da7c07ae66f24deb7211171d2 Mon Sep 17 00:00:00 2001
From: jbrockmendel <jbrockmendel@gmail.com>
Date: Mon, 3 Feb 2020 20:50:14 -0800
Subject: [PATCH 2/5] revert non-central

---
 pandas/core/indexes/base.py                 |  6 ++--
 pandas/core/indexes/category.py             | 38 +++++++++++++++++++--
 pandas/core/indexes/extension.py            | 23 -------------
 pandas/tests/indexes/multi/test_indexing.py |  2 +-
 pandas/tests/indexes/test_numeric.py        |  2 +-
 pandas/tests/indexing/test_floats.py        | 12 +++----
 6 files changed, 47 insertions(+), 36 deletions(-)

diff --git a/pandas/core/indexes/base.py b/pandas/core/indexes/base.py
index 7fdf137416774..72ccaca8a12d1 100644
--- a/pandas/core/indexes/base.py
+++ b/pandas/core/indexes/base.py
@@ -2889,9 +2889,9 @@ def get_loc(self, key, method=None, tolerance=None):
                     "backfill or nearest lookups"
                 )
             try:
-                return self._engine.get_loc(self._maybe_cast_indexer(key))
+                return self._engine.get_loc(key)
             except KeyError:
-                raise KeyError(key)
+                return self._engine.get_loc(self._maybe_cast_indexer(key))
 
         if tolerance is not None:
             tolerance = self._convert_tolerance(tolerance, np.asarray(key))
@@ -4604,7 +4604,7 @@ def get_value(self, series: "Series", key):
             # If that fails, raise a KeyError if an integer
             # index, otherwise, see if key is an integer, and
             # try that
-            loc = self._engine.get_loc(key)
+            loc = self.get_loc(key)
         except KeyError:
             if len(self) > 0 and (self.holds_integer() or self.is_boolean()):
                 raise
diff --git a/pandas/core/indexes/category.py b/pandas/core/indexes/category.py
index e87275a5a20f3..2cdf47ad61cec 100644
--- a/pandas/core/indexes/category.py
+++ b/pandas/core/indexes/category.py
@@ -450,10 +450,44 @@ def _to_safe_for_reshape(self):
         """ convert to object if we are a categorical """
         return self.astype("object")
 
-    def _maybe_cast_indexer(self, key):
+    def get_loc(self, key, method=None):
+        """
+        Get integer location, slice or boolean mask for requested label.
+
+        Parameters
+        ----------
+        key : label
+        method : {None}
+            * default: exact matches only.
+
+        Returns
+        -------
+        loc : int if unique index, slice if monotonic index, else mask
+
+        Raises
+        ------
+        KeyError : if the key is not in the index
+
+        Examples
+        --------
+        >>> unique_index = pd.CategoricalIndex(list('abc'))
+        >>> unique_index.get_loc('b')
+        1
+
+        >>> monotonic_index = pd.CategoricalIndex(list('abbc'))
+        >>> monotonic_index.get_loc('b')
+        slice(1, 3, None)
+
+        >>> non_monotonic_index = pd.CategoricalIndex(list('abcb'))
+        >>> non_monotonic_index.get_loc('b')
+        array([False,  True, False,  True], dtype=bool)
+        """
         code = self.categories.get_loc(key)
         code = self.codes.dtype.type(code)
-        return code
+        try:
+            return self._engine.get_loc(code)
+        except KeyError:
+            raise KeyError(key)
 
     def get_value(self, series: "Series", key: Any):
         """
diff --git a/pandas/core/indexes/extension.py b/pandas/core/indexes/extension.py
index c32889a9360bc..80f2575541767 100644
--- a/pandas/core/indexes/extension.py
+++ b/pandas/core/indexes/extension.py
@@ -297,26 +297,3 @@ def astype(self, dtype, copy=True):
         # pass copy=False because any copying will be done in the
         #  _data.astype call above
         return Index(new_values, dtype=new_values.dtype, name=self.name, copy=False)
-
-    # --------------------------------------------------------------------
-    # Indexing Methods
-
-    @Appender(Index.get_value.__doc__)
-    def get_value(self, series: "Series", key):
-        """
-        Fast lookup of value from 1-dimensional ndarray. Only use this if you
-        know what you're doing
-        """
-        try:
-            loc = self.get_loc(key)
-        except KeyError:
-            # e.g. DatetimeIndex doesn't hold integers
-            if is_integer(key) and not self.holds_integer():
-                # Fall back to positional
-                loc = key
-            else:
-                raise
-
-        return self._get_values_for_loc(series, loc)
-
-    # --------------------------------------------------------------------
diff --git a/pandas/tests/indexes/multi/test_indexing.py b/pandas/tests/indexes/multi/test_indexing.py
index 21a4773fa3683..b08280a712642 100644
--- a/pandas/tests/indexes/multi/test_indexing.py
+++ b/pandas/tests/indexes/multi/test_indexing.py
@@ -392,7 +392,7 @@ def test_get_loc_missing_nan():
     # GH 8569
     idx = MultiIndex.from_arrays([[1.0, 2.0], [3.0, 4.0]])
     assert isinstance(idx.get_loc(1), slice)
-    with pytest.raises(KeyError, match=r"^3$"):
+    with pytest.raises(KeyError, match=r"^3\.0$"):
         idx.get_loc(3)
     with pytest.raises(KeyError, match=r"^nan$"):
         idx.get_loc(np.nan)
diff --git a/pandas/tests/indexes/test_numeric.py b/pandas/tests/indexes/test_numeric.py
index 1b504ce99604d..992a91ad8a528 100644
--- a/pandas/tests/indexes/test_numeric.py
+++ b/pandas/tests/indexes/test_numeric.py
@@ -385,7 +385,7 @@ def test_get_loc_missing_nan(self):
         # GH 8569
         idx = Float64Index([1, 2])
         assert idx.get_loc(1) == 0
-        with pytest.raises(KeyError, match=r"^3$"):
+        with pytest.raises(KeyError, match=r"^3\.0$"):
             idx.get_loc(3)
         with pytest.raises(KeyError, match="^nan$"):
             idx.get_loc(np.nan)
diff --git a/pandas/tests/indexing/test_floats.py b/pandas/tests/indexing/test_floats.py
index 89647e87445fc..5530896a90941 100644
--- a/pandas/tests/indexing/test_floats.py
+++ b/pandas/tests/indexing/test_floats.py
@@ -107,7 +107,7 @@ def test_scalar_non_numeric(self):
                     "mixed",
                 }:
                     error = KeyError
-                    msg = r"^3\.0$"
+                    msg = r"^3$"
                 else:
                     error = TypeError
                     msg = (
@@ -187,7 +187,7 @@ def test_scalar_with_mixed(self):
             with pytest.raises(TypeError, match=msg):
                 idxr(s2)[1.0]
 
-        with pytest.raises(KeyError, match=r"^1\.0$"):
+        with pytest.raises(KeyError, match=r"^1$"):
             s2.loc[1.0]
 
         result = s2.loc["b"]
@@ -213,7 +213,7 @@ def test_scalar_with_mixed(self):
         msg = "Cannot index by location index with a non-integer key"
         with pytest.raises(TypeError, match=msg):
             s3.iloc[1.0]
-        with pytest.raises(KeyError, match=r"^1\.0$"):
+        with pytest.raises(KeyError, match=r"^1$"):
             s3.loc[1.0]
 
         result = s3.loc[1.5]
@@ -666,11 +666,11 @@ def test_floating_misc(self):
         # value not found (and no fallbacking at all)
 
         # scalar integers
-        with pytest.raises(KeyError, match=r"^4$"):
+        with pytest.raises(KeyError, match=r"^4\.0$"):
             s.loc[4]
-        with pytest.raises(KeyError, match=r"^4$"):
+        with pytest.raises(KeyError, match=r"^4\.0$"):
             s.loc[4]
-        with pytest.raises(KeyError, match=r"^4$"):
+        with pytest.raises(KeyError, match=r"^4\.0$"):
             s[4]
 
         # fancy floats/integers create the correct entry (as nan)

From ad1c0f769ecfdbeb81403e382a0a985c461ceaee Mon Sep 17 00:00:00 2001
From: jbrockmendel <jbrockmendel@gmail.com>
Date: Wed, 5 Feb 2020 09:39:38 -0800
Subject: [PATCH 3/5] REF: Index.get_value call self.get_loc instead of
 self._engine.get_loc

---
 pandas/core/indexes/base.py     | 10 +++++++++-
 pandas/core/indexes/interval.py |  7 ++++---
 pandas/core/indexes/numeric.py  | 26 ++++++++++----------------
 3 files changed, 23 insertions(+), 20 deletions(-)

diff --git a/pandas/core/indexes/base.py b/pandas/core/indexes/base.py
index 45dad7c50092e..3c735fc0309b6 100644
--- a/pandas/core/indexes/base.py
+++ b/pandas/core/indexes/base.py
@@ -4592,7 +4592,7 @@ def get_value(self, series: "Series", key):
             # try that
             loc = self.get_loc(key)
         except KeyError:
-            if len(self) > 0 and (self.holds_integer() or self.is_boolean()):
+            if not self._should_fallback_to_positional():
                 raise
             elif is_integer(key):
                 # If the Index cannot hold integer, then this is unambiguously
@@ -4603,6 +4603,14 @@ def get_value(self, series: "Series", key):
 
         return self._get_values_for_loc(series, loc)
 
+    def _should_fallback_to_positional(self) -> bool:
+        """
+        If an integer key is not found, should we fall back to positional indexing?
+        """
+        if len(self) > 0 and (self.holds_integer() or self.is_boolean()):
+            return False
+        return True
+
     def _get_values_for_loc(self, series: "Series", loc):
         """
         Do a positional lookup on the given Series, returning either a scalar
diff --git a/pandas/core/indexes/interval.py b/pandas/core/indexes/interval.py
index 0252a13665b84..9ec72df140c85 100644
--- a/pandas/core/indexes/interval.py
+++ b/pandas/core/indexes/interval.py
@@ -523,9 +523,10 @@ def is_overlapping(self) -> bool:
         # GH 23309
         return self._engine.is_overlapping
 
-    def holds_integer(self):
-        return self.dtype.subtype.kind not in ["m", "M"]
-        # TODO: There must already exist something for this?
+    def _should_fallback_to_positional(self):
+        # integer lookups in Series.__getitem__ are unambiguously
+        #  positional in this case
+        return self.dtype.subtype.kind in ["m", "M"]
 
     @Appender(Index._convert_scalar_indexer.__doc__)
     def _convert_scalar_indexer(self, key, kind=None):
diff --git a/pandas/core/indexes/numeric.py b/pandas/core/indexes/numeric.py
index ebfe50327b479..5c332d16e4765 100644
--- a/pandas/core/indexes/numeric.py
+++ b/pandas/core/indexes/numeric.py
@@ -1,4 +1,4 @@
-from typing import TYPE_CHECKING, Any
+from typing import Any
 
 import numpy as np
 
@@ -32,12 +32,9 @@
 
 from pandas.core import algorithms
 import pandas.core.common as com
-from pandas.core.indexes.base import Index, InvalidIndexError, maybe_extract_name
+from pandas.core.indexes.base import Index, maybe_extract_name
 from pandas.core.ops import get_op_result_name
 
-if TYPE_CHECKING:
-    from pandas import Series
-
 _num_index_shared_docs = dict()
 
 
@@ -383,6 +380,12 @@ def astype(self, dtype, copy=True):
             return Int64Index(arr)
         return super().astype(dtype, copy=copy)
 
+    # ----------------------------------------------------------------
+    # Indexing Methods
+
+    def _should_fallback_to_positional(self):
+        return False
+
     @Appender(Index._convert_scalar_indexer.__doc__)
     def _convert_scalar_indexer(self, key, kind=None):
         assert kind in ["loc", "getitem", "iloc", None]
@@ -401,6 +404,8 @@ def _convert_slice_indexer(self, key: slice, kind=None):
         # translate to locations
         return self.slice_indexer(key.start, key.stop, key.step, kind=kind)
 
+    # ----------------------------------------------------------------
+
     def _format_native_types(
         self, na_rep="", float_format=None, decimal=".", quoting=None, **kwargs
     ):
@@ -416,17 +421,6 @@ def _format_native_types(
         )
         return formatter.get_result_as_array()
 
-    @Appender(Index.get_value.__doc__)
-    def get_value(self, series: "Series", key):
-        """
-        We always want to get an index value, never a value.
-        """
-        if not is_scalar(key):
-            raise InvalidIndexError
-
-        loc = self.get_loc(key)
-        return self._get_values_for_loc(series, loc)
-
     def equals(self, other) -> bool:
         """
         Determines if two Index objects contain the same elements.

From 16b064cf5300bb83276d8eeeccbde0a3fa6281e0 Mon Sep 17 00:00:00 2001
From: jbrockmendel <jbrockmendel@gmail.com>
Date: Wed, 5 Feb 2020 10:05:50 -0800
Subject: [PATCH 4/5] fixup remove unused imports

---
 pandas/core/indexes/extension.py | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/pandas/core/indexes/extension.py b/pandas/core/indexes/extension.py
index 80f2575541767..66b551f654bf1 100644
--- a/pandas/core/indexes/extension.py
+++ b/pandas/core/indexes/extension.py
@@ -1,7 +1,7 @@
 """
 Shared methods for Index subclasses backed by ExtensionArray.
 """
-from typing import TYPE_CHECKING, List
+from typing import List
 
 import numpy as np
 
@@ -11,7 +11,6 @@
 from pandas.core.dtypes.common import (
     ensure_platform_int,
     is_dtype_equal,
-    is_integer,
     is_object_dtype,
 )
 from pandas.core.dtypes.generic import ABCSeries
@@ -21,9 +20,6 @@
 from pandas.core.indexes.base import Index
 from pandas.core.ops import get_op_result_name
 
-if TYPE_CHECKING:
-    from pandas import Series
-
 
 def inherit_from_data(name: str, delegate, cache: bool = False, wrap: bool = False):
     """

From 6b0218411983a5989b2a386c1440280ffe6fa16f Mon Sep 17 00:00:00 2001
From: jbrockmendel <jbrockmendel@gmail.com>
Date: Wed, 5 Feb 2020 18:02:59 -0800
Subject: [PATCH 5/5] inherit docstring

---
 pandas/core/indexes/numeric.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/pandas/core/indexes/numeric.py b/pandas/core/indexes/numeric.py
index 5c332d16e4765..2f4c48cc2e5a5 100644
--- a/pandas/core/indexes/numeric.py
+++ b/pandas/core/indexes/numeric.py
@@ -383,6 +383,7 @@ def astype(self, dtype, copy=True):
     # ----------------------------------------------------------------
     # Indexing Methods
 
+    @Appender(Index._should_fallback_to_positional.__doc__)
     def _should_fallback_to_positional(self):
         return False