REF: Refactor signature of RangeIndex._simple_new (#26722)

Author: topper-123

doc/source/whatsnew/v0.25.0.rst

@@ -525,7 +525,7 @@ Performance Improvements
 - Improved performance of :meth:`Series.searchsorted`. The speedup is especially large when the dtype is
   int8/int16/int32 and the searched key is within the integer bounds for the dtype (:issue:`22034`)
 - Improved performance of :meth:`pandas.core.groupby.GroupBy.quantile` (:issue:`20405`)
-- Improved performance of slicing and other selected operation on a :class:`RangeIndex` (:issue:`26565`, :issue:`26617`)
+- Improved performance of slicing and other selected operation on a :class:`RangeIndex` (:issue:`26565`, :issue:`26617`, :issue:`26722`)
 - Improved performance of :meth:`read_csv` by faster tokenizing and faster parsing of small float numbers (:issue:`25784`)
 - Improved performance of :meth:`read_csv` by faster parsing of N/A and boolean values (:issue:`25804`)
 - Improved performance of :attr:`IntervalIndex.is_monotonic`, :attr:`IntervalIndex.is_monotonic_increasing` and :attr:`IntervalIndex.is_monotonic_decreasing` by removing conversion to :class:`MultiIndex` (:issue:`24813`)

pandas/core/indexes/base.py

@@ -273,8 +273,7 @@ def __new__(cls, data=None, dtype=None, copy=False, name=None,
         if isinstance(data, RangeIndex):
             return RangeIndex(start=data, copy=copy, dtype=dtype, name=name)
         elif isinstance(data, range):
-            return RangeIndex.from_range(data, copy=copy, dtype=dtype,
-                                         name=name)
+            return RangeIndex.from_range(data, dtype=dtype, name=name)
 
         # categorical
         elif is_categorical_dtype(data) or is_categorical_dtype(dtype):

pandas/core/indexes/range.py

@@ -6,7 +6,7 @@
 
 import numpy as np
 
-from pandas._libs import index as libindex, lib
+from pandas._libs import index as libindex
 import pandas.compat as compat
 from pandas.compat.numpy import function as nv
 from pandas.util._decorators import Appender, cache_readonly
@@ -82,16 +82,15 @@ def __new__(cls, start=None, stop=None, step=None,
                           "removed in a future version.",
                           FutureWarning, stacklevel=2)
             if fastpath:
-                return cls._simple_new(start, stop, step, name=name)
+                return cls._simple_new(range(start, stop, step), name=name)
 
         cls._validate_dtype(dtype)
 
         # RangeIndex
         if isinstance(start, RangeIndex):
-            if name is None:
-                name = start.name
-            return cls._simple_new(name=name,
-                                   **dict(start._get_data_as_items()))
+            name = start.name if name is None else name
+            start = start._range
+            return cls._simple_new(start, dtype=dtype, name=name)
 
         # validate the arguments
         if com._all_none(start, stop, step):
@@ -108,10 +107,11 @@ def __new__(cls, start=None, stop=None, step=None,
         if step == 0:
             raise ValueError("Step must not be zero")
 
-        return cls._simple_new(start, stop, step, name)
+        rng = range(start, stop, step)
+        return cls._simple_new(rng, dtype=dtype, name=name)
 
     @classmethod
-    def from_range(cls, data, name=None, dtype=None, **kwargs):
+    def from_range(cls, data, name=None, dtype=None):
         """
         Create RangeIndex from a range object.
 
@@ -124,26 +124,21 @@ def from_range(cls, data, name=None, dtype=None, **kwargs):
                 '{0}(...) must be called with object coercible to a '
                 'range, {1} was passed'.format(cls.__name__, repr(data)))
 
-        start, stop, step = data.start, data.stop, data.step
-        return cls(start, stop, step, dtype=dtype, name=name, **kwargs)
+        cls._validate_dtype(dtype)
+        return cls._simple_new(data, dtype=dtype, name=name)
 
     @classmethod
-    def _simple_new(cls, start, stop=None, step=None, name=None,
-                    dtype=None, **kwargs):
+    def _simple_new(cls, values, name=None, dtype=None, **kwargs):
         result = object.__new__(cls)
 
         # handle passed None, non-integers
-        if start is None and stop is None:
+        if values is None:
             # empty
-            start, stop, step = 0, 0, 1
+            values = range(0, 0, 1)
+        elif not isinstance(values, range):
+            return Index(values, dtype=dtype, name=name, **kwargs)
 
-        if start is None or not is_integer(start):
-            try:
-                return cls(start, stop, step, name=name, **kwargs)
-            except TypeError:
-                return Index(start, stop, step, name=name, **kwargs)
-
-        result._range = range(start, stop or 0, step or 1)
+        result._range = values
 
         result.name = name
         for k, v in kwargs.items():
@@ -360,8 +355,7 @@ def tolist(self):
     def _shallow_copy(self, values=None, **kwargs):
         if values is None:
             name = kwargs.get("name", self.name)
-            return self._simple_new(
-                name=name, **dict(self._get_data_as_items()))
+            return self._simple_new(self._range, name=name)
         else:
             kwargs.setdefault('name', self.name)
             return self._int64index._shallow_copy(values, **kwargs)
@@ -480,11 +474,13 @@ def intersection(self, other, sort=False):
         tmp_start = first.start + (second.start - first.start) * \
             first.step // gcd * s
         new_step = first.step * second.step // gcd
-        new_index = self._simple_new(tmp_start, int_high, new_step)
+        new_range = range(tmp_start, int_high, new_step)
+        new_index = self._simple_new(new_range)
 
         # adjust index to limiting interval
         new_start = new_index._min_fitting_element(int_low)
-        new_index = self._simple_new(new_start, new_index.stop, new_index.step)
+        new_range = range(new_start, new_index.stop, new_index.step)
+        new_index = self._simple_new(new_range)
 
         if (self.step < 0 and other.step < 0) is not (new_index.step < 0):
             new_index = new_index[::-1]
@@ -609,23 +605,22 @@ def __getitem__(self, key):
         """
         Conserve RangeIndex type for scalar and slice keys.
         """
-        if is_scalar(key):
-            if not lib.is_integer(key):
-                raise IndexError("only integers, slices (`:`), "
-                                 "ellipsis (`...`), numpy.newaxis (`None`) "
-                                 "and integer or boolean "
-                                 "arrays are valid indices")
+        if isinstance(key, slice):
+            new_range = self._range[key]
+            return self._simple_new(new_range, name=self.name)
+        elif is_integer(key):
             new_key = int(key)
             try:
                 return self._range[new_key]
             except IndexError:
                 raise IndexError("index {key} is out of bounds for axis 0 "
                                  "with size {size}".format(key=key,
                                                            size=len(self)))
-        if isinstance(key, slice):
-            new_range = self._range[key]
-            return self.from_range(new_range, name=self.name)
-
+        elif is_scalar(key):
+            raise IndexError("only integers, slices (`:`), "
+                             "ellipsis (`...`), numpy.newaxis (`None`) "
+                             "and integer or boolean "
+                             "arrays are valid indices")
         # fall back to Int64Index
         return super().__getitem__(key)
 
@@ -640,10 +635,12 @@ def __floordiv__(self, other):
                 start = self.start // other
                 step = self.step // other
                 stop = start + len(self) * step
-                return self._simple_new(start, stop, step, name=self.name)
+                new_range = range(start, stop, step or 1)
+                return self._simple_new(new_range, name=self.name)
             if len(self) == 1:
                 start = self.start // other
-                return self._simple_new(start, start + 1, 1, name=self.name)
+                new_range = range(start, start + 1, 1)
+                return self._simple_new(new_range, name=self.name)
         return self._int64index // other
 
     def all(self) -> bool:

pandas/tests/indexes/test_range.py

@@ -94,8 +94,9 @@ def test_constructor_same(self):
 
     def test_constructor_range(self):
 
-        with pytest.raises(TypeError):
-            RangeIndex(range(1, 5, 2))
+        msg = "Value needs to be a scalar value, was type <class 'range'>"
+        with pytest.raises(TypeError, match=msg):
+            result = RangeIndex(range(1, 5, 2))
 
         result = RangeIndex.from_range(range(1, 5, 2))
         expected = RangeIndex(1, 5, 2)
@@ -120,6 +121,9 @@ def test_constructor_range(self):
 
         with pytest.raises(TypeError):
             Index(range(1, 5, 2), dtype='float64')
+        msg = r'^from_range\(\) got an unexpected keyword argument'
+        with pytest.raises(TypeError, match=msg):
+            pd.RangeIndex.from_range(range(10), copy=True)
 
     def test_constructor_name(self):
         # GH12288