TYP: Arraylike

pandas/core/arrays/base.py

@@ -49,6 +49,7 @@ class ExtensionArray:
     nbytes
     ndim
     shape
+    size
 
     Methods
     -------
@@ -439,7 +440,7 @@ def isna(self) -> ArrayLike:
 
         Returns
         -------
-        na_values : Union[np.ndarray, ExtensionArray]
+        na_values : np.ndarray or ExtensionArray
             In most cases, this should return a NumPy ndarray. For
             exceptional cases like ``SparseArray``, where returning
             an ndarray would be expensive, an ExtensionArray may be

pandas/core/base.py

@@ -4,11 +4,12 @@
 
 import builtins
 import textwrap
-from typing import Any, Dict, FrozenSet, List, Optional, Union
+from typing import Any, Dict, FrozenSet, Generic, List, Optional
 
 import numpy as np
 
 import pandas._libs.lib as lib
+from pandas._typing import ArrayLike
 from pandas.compat import PYPY
 from pandas.compat.numpy import function as nv
 from pandas.errors import AbstractMethodError
@@ -584,7 +585,7 @@ def _shallow_copy(self, obj, **kwargs):
         return self._constructor(obj, **kwargs)
 
 
-class IndexOpsMixin:
+class IndexOpsMixin(Generic[ArrayLike]):
     """
     Common ops mixin to support a unified interface / docs for Series / Index
     """
@@ -596,7 +597,7 @@ class IndexOpsMixin:
     )
 
     @property
-    def _values(self) -> Union[ExtensionArray, np.ndarray]:
+    def _values(self) -> ArrayLike:
         # must be defined here as a property for mypy
         raise AbstractMethodError(self)
 
@@ -1141,7 +1142,10 @@ def _map_values(self, mapper, na_action=None):
             values = self._values
             if na_action is not None:
                 raise NotImplementedError
-            map_f = lambda values, f: values.map(f)
+
+            def map_f(values, f):
+                return values.map(f)
+
         else:
             values = self.astype(object)
             values = getattr(values, "values", values)

pandas/core/indexes/base.py

@@ -13,7 +13,7 @@
 from pandas._libs.tslibs import OutOfBoundsDatetime, Timestamp
 from pandas._libs.tslibs.period import IncompatibleFrequency
 from pandas._libs.tslibs.timezones import tz_compare
-from pandas._typing import Label
+from pandas._typing import ArrayLike, Label
 from pandas.compat import set_function_name
 from pandas.compat.numpy import function as nv
 from pandas.util._decorators import Appender, Substitution, cache_readonly, doc
@@ -183,7 +183,7 @@ def _new_Index(cls, d):
     return cls.__new__(cls, **d)
 
 
-class Index(IndexOpsMixin, PandasObject):
+class Index(IndexOpsMixin[ArrayLike], PandasObject):
     """
     Immutable ndarray implementing an ordered, sliceable set. The basic object
     storing axis labels for all pandas objects.
@@ -255,7 +255,7 @@ def _outer_indexer(self, left, right):
         return libjoin.outer_join_indexer(left, right)
 
     _typ = "index"
-    _data: Union[ExtensionArray, np.ndarray]
+    _data: ArrayLike
     _id = None
     _name: Label = None
     # MultiIndex.levels previously allowed setting the index name. We
@@ -3855,7 +3855,7 @@ def array(self) -> ExtensionArray:
         return array
 
     @property
-    def _values(self) -> Union[ExtensionArray, np.ndarray]:
+    def _values(self) -> ArrayLike:
         """
         The best array representation.
 

pandas/core/indexes/period.py

@@ -230,7 +230,10 @@ def _simple_new(cls, values: PeriodArray, name: Label = None):
             Values that can be converted to a PeriodArray without inference
             or coercion.
         """
-        assert isinstance(values, PeriodArray), type(values)
+        if not isinstance(values, PeriodArray):
+            raise TypeError(
+                f"_simple_new expects PeriodArray, got {type(values).__name__}"
+            )
 
         result = object.__new__(cls)
         result._data = values

pandas/tests/indexes/period/test_constructors.py

@@ -321,7 +321,9 @@ def test_constructor_mixed(self):
     def test_constructor_simple_new(self):
         idx = period_range("2007-01", name="p", periods=2, freq="M")
 
-        with pytest.raises(AssertionError, match="<class .*PeriodIndex'>"):
+        with pytest.raises(
+            TypeError, match="_simple_new expects PeriodArray, got PeriodIndex"
+        ):
             idx._simple_new(idx, name="p")
 
         result = idx._simple_new(idx._data, name="p")
@@ -339,15 +341,21 @@ def test_constructor_simple_new(self):
     def test_constructor_simple_new_empty(self):
         # GH13079
         idx = PeriodIndex([], freq="M", name="p")
-        with pytest.raises(AssertionError, match="<class .*PeriodIndex'>"):
+        with pytest.raises(
+            TypeError, match="_simple_new expects PeriodArray, got PeriodIndex"
+        ):
             idx._simple_new(idx, name="p")
 
         result = idx._simple_new(idx._data, name="p")
         tm.assert_index_equal(result, idx)
 
-    @pytest.mark.parametrize("floats", [[1.1, 2.1], np.array([1.1, 2.1])])
-    def test_constructor_floats(self, floats):
-        with pytest.raises(AssertionError, match="<class "):
+    @pytest.mark.parametrize(
+        "floats,box", [([1.1, 2.1], "list"), (np.array([1.1, 2.1]), "ndarray")]
+    )
+    def test_constructor_floats(self, floats, box):
+        with pytest.raises(
+            TypeError, match=f"_simple_new expects PeriodArray, got {box}"
+        ):
             PeriodIndex._simple_new(floats)
 
         msg = "PeriodIndex does not allow floating point in construction"

pandas/tests/indexes/period/test_period.py

@@ -92,12 +92,16 @@ def test_shallow_copy_empty(self):
     def test_shallow_copy_disallow_i8(self):
         # GH-24391
         pi = period_range("2018-01-01", periods=3, freq="2D")
-        with pytest.raises(AssertionError, match="ndarray"):
+        with pytest.raises(
+            TypeError, match="_simple_new expects PeriodArray, got ndarray"
+        ):
             pi._shallow_copy(pi.asi8)
 
     def test_shallow_copy_requires_disallow_period_index(self):
         pi = period_range("2018-01-01", periods=3, freq="2D")
-        with pytest.raises(AssertionError, match="PeriodIndex"):
+        with pytest.raises(
+            TypeError, match="_simple_new expects PeriodArray, got PeriodIndex"
+        ):
             pi._shallow_copy(pi)
 
     def test_view_asi8(self):