REF: simplify Index.__new__ (pandas-dev#38910)

Author: jbrockmendel

pandas/core/indexes/base.py

@@ -6,6 +6,7 @@
     TYPE_CHECKING,
     Any,
     Callable,
+    Dict,
     FrozenSet,
     Hashable,
     List,
@@ -131,6 +132,11 @@
 _Identity = NewType("_Identity", object)
 
 
+def disallow_kwargs(kwargs: Dict[str, Any]):
+    if kwargs:
+        raise TypeError(f"Unexpected keyword arguments {repr(set(kwargs))}")
+
+
 def _new_Index(cls, d):
     """
     This is called upon unpickling, rather than the default which doesn't
@@ -296,32 +302,29 @@ def __new__(
                 return result.astype(dtype, copy=False)
             return result
 
-        if is_ea_or_datetimelike_dtype(dtype):
+        elif is_ea_or_datetimelike_dtype(dtype):
             # non-EA dtype indexes have special casting logic, so we punt here
             klass = cls._dtype_to_subclass(dtype)
             if klass is not Index:
                 return klass(data, dtype=dtype, copy=copy, name=name, **kwargs)
 
-        if is_ea_or_datetimelike_dtype(data_dtype):
+            ea_cls = dtype.construct_array_type()
+            data = ea_cls._from_sequence(data, dtype=dtype, copy=copy)
+            data = np.asarray(data, dtype=object)
+            disallow_kwargs(kwargs)
+            return Index._simple_new(data, name=name)
+
+        elif is_ea_or_datetimelike_dtype(data_dtype):
             klass = cls._dtype_to_subclass(data_dtype)
             if klass is not Index:
                 result = klass(data, copy=copy, name=name, **kwargs)
                 if dtype is not None:
                     return result.astype(dtype, copy=False)
                 return result
 
-        # extension dtype
-        if is_extension_array_dtype(data_dtype) or is_extension_array_dtype(dtype):
-            if not (dtype is None or is_object_dtype(dtype)):
-                # coerce to the provided dtype
-                ea_cls = dtype.construct_array_type()
-                data = ea_cls._from_sequence(data, dtype=dtype, copy=False)
-            else:
-                data = np.asarray(data, dtype=object)
-
-            # coerce to the object dtype
-            data = data.astype(object)
-            return Index(data, dtype=object, copy=copy, name=name, **kwargs)
+            data = np.array(data, dtype=object, copy=copy)
+            disallow_kwargs(kwargs)
+            return Index._simple_new(data, name=name)
 
         # index-like
         elif isinstance(data, (np.ndarray, Index, ABCSeries)):
@@ -333,7 +336,7 @@ def __new__(
                 # should not be coerced
                 # GH 11836
                 data = _maybe_cast_with_dtype(data, dtype, copy)
-                dtype = data.dtype  # TODO: maybe not for object?
+                dtype = data.dtype
 
             if data.dtype.kind in ["i", "u", "f"]:
                 # maybe coerce to a sub-class
@@ -342,16 +345,15 @@ def __new__(
                 arr = com.asarray_tuplesafe(data, dtype=object)
 
                 if dtype is None:
-                    new_data = _maybe_cast_data_without_dtype(arr)
-                    new_dtype = new_data.dtype
-                    return cls(
-                        new_data, dtype=new_dtype, copy=copy, name=name, **kwargs
-                    )
+                    arr = _maybe_cast_data_without_dtype(arr)
+                    dtype = arr.dtype
+
+                    if kwargs:
+                        return cls(arr, dtype, copy=copy, name=name, **kwargs)
 
             klass = cls._dtype_to_subclass(arr.dtype)
             arr = klass._ensure_array(arr, dtype, copy)
-            if kwargs:
-                raise TypeError(f"Unexpected keyword arguments {repr(set(kwargs))}")
+            disallow_kwargs(kwargs)
             return klass._simple_new(arr, name)
 
         elif is_scalar(data):

pandas/core/indexes/datetimelike.py

@@ -623,7 +623,7 @@ def _convert_arr_indexer(self, keyarr):
             return com.asarray_tuplesafe(keyarr)
 
 
-class DatetimeTimedeltaMixin(DatetimeIndexOpsMixin, Int64Index):
+class DatetimeTimedeltaMixin(DatetimeIndexOpsMixin):
     """
     Mixin class for methods shared by DatetimeIndex and TimedeltaIndex,
     but not PeriodIndex
@@ -816,11 +816,7 @@ def _union(self, other, sort):
             i8self = Int64Index._simple_new(self.asi8)
             i8other = Int64Index._simple_new(other.asi8)
             i8result = i8self._union(i8other, sort=sort)
-            # pandas\core\indexes\datetimelike.py:887: error: Unexpected
-            # keyword argument "freq" for "DatetimeTimedeltaMixin"  [call-arg]
-            result = type(self)(
-                i8result, dtype=self.dtype, freq="infer"  # type: ignore[call-arg]
-            )
+            result = type(self)(i8result, dtype=self.dtype, freq="infer")
             return result
 
     # --------------------------------------------------------------------