From 2ce2f4ffe2251117bff87311118e82feba05a258 Mon Sep 17 00:00:00 2001
From: Kyle Goehner <kgoehner@amazon.com>
Date: Wed, 16 Oct 2019 21:47:21 -0400
Subject: [PATCH] CLN: Use ABC classes where possible

---
 pandas/core/indexes/base.py   | 15 ++++++++++-----
 pandas/core/reshape/concat.py | 14 ++++++++------
 2 files changed, 18 insertions(+), 11 deletions(-)

diff --git a/pandas/core/indexes/base.py b/pandas/core/indexes/base.py
index 9d6487f7a8ae4..21882a8f132d8 100644
--- a/pandas/core/indexes/base.py
+++ b/pandas/core/indexes/base.py
@@ -53,6 +53,7 @@
     ABCDataFrame,
     ABCDatetimeArray,
     ABCDatetimeIndex,
+    ABCExtensionArray,
     ABCIndexClass,
     ABCMultiIndex,
     ABCPandasArray,
@@ -65,7 +66,6 @@
 from pandas.core import ops
 from pandas.core.accessor import CachedAccessor
 import pandas.core.algorithms as algos
-from pandas.core.arrays import ExtensionArray
 from pandas.core.base import IndexOpsMixin, PandasObject
 import pandas.core.common as com
 from pandas.core.indexers import maybe_convert_indices
@@ -100,7 +100,7 @@
 
 def _make_comparison_op(op, cls):
     def cmp_method(self, other):
-        if isinstance(other, (np.ndarray, Index, ABCSeries, ExtensionArray)):
+        if isinstance(other, (np.ndarray, Index, ABCSeries, ABCExtensionArray)):
             if other.ndim > 0 and len(self) != len(other):
                 raise ValueError("Lengths must match to compare")
 
@@ -3840,7 +3840,7 @@ def values(self):
         return self._data.view(np.ndarray)
 
     @property
-    def _values(self) -> Union[ExtensionArray, ABCIndexClass, np.ndarray]:
+    def _values(self) -> Union[ABCExtensionArray, ABCIndexClass, np.ndarray]:
         # TODO(EA): remove index types as they become extension arrays
         """
         The best array representation.
@@ -4268,7 +4268,12 @@ def _concat_same_dtype(self, to_concat, name):
         Concatenate to_concat which has the same class.
         """
         # must be overridden in specific classes
-        klasses = (ABCDatetimeIndex, ABCTimedeltaIndex, ABCPeriodIndex, ExtensionArray)
+        klasses = (
+            ABCDatetimeIndex,
+            ABCTimedeltaIndex,
+            ABCPeriodIndex,
+            ABCExtensionArray,
+        )
         to_concat = [
             x.astype(object) if isinstance(x, klasses) else x for x in to_concat
         ]
@@ -4631,7 +4636,7 @@ def get_value(self, series, key):
         # use this, e.g. DatetimeIndex
         # Things like `Series._get_value` (via .at) pass the EA directly here.
         s = getattr(series, "_values", series)
-        if isinstance(s, (ExtensionArray, Index)) and is_scalar(key):
+        if isinstance(s, (ABCExtensionArray, Index)) and is_scalar(key):
             # GH 20882, 21257
             # Unify Index and ExtensionArray treatment
             # First try to convert the key to a location
diff --git a/pandas/core/reshape/concat.py b/pandas/core/reshape/concat.py
index 60bab817705e3..243eb9e99e1f8 100644
--- a/pandas/core/reshape/concat.py
+++ b/pandas/core/reshape/concat.py
@@ -6,7 +6,9 @@
 
 import numpy as np
 
-from pandas import DataFrame, Index, MultiIndex, Series
+from pandas.core.dtypes.generic import ABCSeries
+
+from pandas import DataFrame, Index, MultiIndex
 from pandas.core import common as com
 from pandas.core.arrays.categorical import (
     _factorize_from_iterable,
@@ -322,7 +324,7 @@ def __init__(
         # consolidate data & figure out what our result ndim is going to be
         ndims = set()
         for obj in objs:
-            if not isinstance(obj, (Series, DataFrame)):
+            if not isinstance(obj, (ABCSeries, DataFrame)):
                 msg = (
                     "cannot concatenate object of type '{}';"
                     " only Series and DataFrame objs are valid".format(type(obj))
@@ -348,7 +350,7 @@ def __init__(
             # filter out the empties if we have not multi-index possibilities
             # note to keep empty Series as it affect to result columns / name
             non_empties = [
-                obj for obj in objs if sum(obj.shape) > 0 or isinstance(obj, Series)
+                obj for obj in objs if sum(obj.shape) > 0 or isinstance(obj, ABCSeries)
             ]
 
             if len(non_empties) and (
@@ -362,7 +364,7 @@ def __init__(
         self.objs = objs
 
         # Standardize axis parameter to int
-        if isinstance(sample, Series):
+        if isinstance(sample, ABCSeries):
             axis = DataFrame._get_axis_number(axis)
         else:
             axis = sample._get_axis_number(axis)
@@ -372,7 +374,7 @@ def __init__(
         if self._is_frame:
             axis = 1 if axis == 0 else 0
 
-        self._is_series = isinstance(sample, Series)
+        self._is_series = isinstance(sample, ABCSeries)
         if not 0 <= axis <= sample.ndim:
             raise AssertionError(
                 "axis must be between 0 and {ndim}, input was"
@@ -545,7 +547,7 @@ def _get_concat_axis(self):
                 num = 0
                 has_names = False
                 for i, x in enumerate(self.objs):
-                    if not isinstance(x, Series):
+                    if not isinstance(x, ABCSeries):
                         raise TypeError(
                             "Cannot concatenate type 'Series' "
                             "with object of type {type!r}".format(type=type(x).__name__)