[WIP] Make Index.values read-only

ci/deps/azure-36-32bit.yaml

@@ -22,5 +22,5 @@ dependencies:
   # see comment above
   - pip
   - pip:
-    - cython>=0.29.16
+    - Cython==3.0a5
     - pytest>=5.0.1,<6.0.0rc0

ci/deps/azure-36-locale.yaml

@@ -6,7 +6,6 @@ dependencies:
   - python=3.6.*
 
   # tools
-  - cython>=0.29.16
   - pytest>=5.0.1,<6.0.0rc0
   - pytest-xdist>=1.21
   - pytest-asyncio
@@ -36,3 +35,6 @@ dependencies:
   - xlsxwriter
   - xlwt
   - moto
+
+  - pip:
+    - Cython==3.0a5

ci/deps/azure-36-locale_slow.yaml

@@ -6,7 +6,6 @@ dependencies:
   - python=3.6.*
 
   # tools
-  - cython>=0.29.16
   - pytest>=5.0.1,<6.0.0rc0
   - pytest-xdist>=1.21
   - hypothesis>=3.58.0
@@ -29,4 +28,5 @@ dependencies:
   - xlwt=1.2.0
   - pip
   - pip:
+    - Cython==3.0a5
     - html5lib==1.0b2

ci/deps/azure-36-minimum_versions.yaml

@@ -5,7 +5,6 @@ dependencies:
   - python=3.6.1
 
   # tools
-  - cython=0.29.16
   - pytest=5.0.1
   - pytest-xdist>=1.21
   - hypothesis>=3.58.0
@@ -28,3 +27,6 @@ dependencies:
   - xlsxwriter=0.9.8
   - xlwt=1.2.0
   - html5lib=1.0.1
+
+  - pip:
+    - Cython==3.0a5

ci/deps/azure-36-slow.yaml

@@ -6,7 +6,6 @@ dependencies:
   - python=3.6.*
 
   # tools
-  - cython>=0.29.16
   - pytest>=5.0.1,<6.0.0rc0
   - pytest-xdist>=1.21
   - hypothesis>=3.58.0
@@ -33,3 +32,5 @@ dependencies:
   - xlsxwriter
   - xlwt
   - moto
+  - pip:
+    - Cython==3.0a5

ci/deps/azure-37-locale.yaml

@@ -5,7 +5,6 @@ dependencies:
   - python=3.7.*
 
   # tools
-  - cython>=0.29.16
   - pytest>=5.0.1,<6.0.0rc0
   - pytest-xdist>=1.21
   - pytest-asyncio
@@ -35,4 +34,5 @@ dependencies:
   - pyarrow>=0.15
   - pip
   - pip:
+    - Cython==3.0a5
     - pyxlsb

ci/deps/azure-37-numpydev.yaml

@@ -14,7 +14,7 @@ dependencies:
   - pytz
   - pip
   - pip:
-    - cython==0.29.16 # GH#34014
+    - Cython==3.0a5
     - "git+git://github.com/dateutil/dateutil.git"
     - "--extra-index-url https://pypi.anaconda.org/scipy-wheels-nightly/simple"
     - "--pre"

ci/deps/azure-macos-36.yaml

@@ -31,6 +31,6 @@ dependencies:
   - xlwt
   - pip
   - pip:
-    - cython>=0.29.16
+    - Cython==3.0a5
     - pyreadstat
     - pyxlsb

ci/deps/azure-windows-36.yaml

@@ -6,7 +6,6 @@ dependencies:
   - python=3.6.*
 
   # tools
-  - cython>=0.29.16
   - pytest>=5.0.1,<6.0.0rc0
   - pytest-xdist>=1.21
   - hypothesis>=3.58.0
@@ -30,3 +29,5 @@ dependencies:
   - xlrd
   - xlsxwriter
   - xlwt
+  - pip:
+    - Cython==3.0a5

ci/deps/azure-windows-37.yaml

@@ -6,7 +6,6 @@ dependencies:
   - python=3.7.*
 
   # tools
-  - cython>=0.29.16
   - pytest>=5.0.1,<6.0.0rc0
   - pytest-xdist>=1.21
   - hypothesis>=3.58.0
@@ -38,4 +37,5 @@ dependencies:
   - pyreadstat
   - pip
   - pip:
+    - Cython==3.0a5
     - pyxlsb

ci/deps/travis-36-cov.yaml

@@ -6,7 +6,6 @@ dependencies:
   - python=3.6.*
 
   # tools
-  - cython>=0.29.16
   - pytest>=5.0.1,<6.0.0rc0
   - pytest-xdist>=1.21
   - hypothesis>=3.58.0
@@ -15,7 +14,6 @@ dependencies:
   # pandas dependencies
   - beautifulsoup4
   - botocore>=1.11
-  - cython>=0.29.16
   - dask
   - fastparquet>=0.3.2
   - fsspec>=0.7.4
@@ -47,6 +45,7 @@ dependencies:
   - xlwt
   - pip
   - pip:
+    - Cython==3.0a5
     - brotlipy
     - coverage
     - pandas-datareader

ci/deps/travis-36-locale.yaml

@@ -6,7 +6,6 @@ dependencies:
   - python=3.6.*
 
   # tools
-  - cython>=0.29.16
   - pytest>=5.0.1,<6.0.0rc0
   - pytest-xdist>=1.21
   - hypothesis>=3.58.0
@@ -38,3 +37,5 @@ dependencies:
   - xlrd
   - xlsxwriter
   - xlwt
+  - pip:
+    - Cython==3.0a5

ci/deps/travis-37-arm64.yaml

@@ -6,7 +6,6 @@ dependencies:
   - python=3.7.*
 
   # tools
-  - cython>=0.29.13
   - pytest>=5.0.1,<6.0.0rc0
   - pytest-xdist>=1.21
   - hypothesis>=3.58.0
@@ -18,4 +17,5 @@ dependencies:
   - pytz
   - pip
   - pip:
+    - Cython==3.0a5
     - moto

ci/deps/travis-37.yaml

@@ -6,7 +6,6 @@ dependencies:
   - python=3.7.*
 
   # tools
-  - cython>=0.29.16
   - pytest>=5.0.1,<6.0.0rc0
   - pytest-xdist>=1.21
   - hypothesis>=3.58.0
@@ -24,4 +23,5 @@ dependencies:
   - pyreadstat
   - pip
   - pip:
+    - Cython==3.0a5
     - moto

ci/deps/travis-38.yaml

@@ -6,7 +6,6 @@ dependencies:
   - python=3.8.*
 
   # tools
-  - cython>=0.29.16
   - pytest>=5.0.1,<6.0.0rc0
   - pytest-xdist>=1.21
   - hypothesis>=3.58.0
@@ -18,3 +17,5 @@ dependencies:
   - pytz
   - pip
   - tabulate==0.8.3
+  - pip:
+    - Cython==3.0a5

pandas/core/arrays/interval.py

@@ -555,13 +555,13 @@ def __setitem__(self, key, value):
 
         # Need to ensure that left and right are updated atomically, so we're
         # forced to copy, update the copy, and swap in the new values.
-        left = self.left.copy(deep=True)
-        left._values[key] = value_left
-        self._left = left
+        left_data = self.left._data.copy()
+        left_data[key] = value_left
+        self._left = self.left._shallow_copy(left_data)
 
-        right = self.right.copy(deep=True)
-        right._values[key] = value_right
-        self._right = right
+        right_data = self.right._data.copy()
+        right_data[key] = value_right
+        self._right = self.right._shallow_copy(right_data)
 
     def __eq__(self, other):
         # ensure pandas array for list-like and eliminate non-interval scalars

pandas/core/indexes/base.py

@@ -3849,7 +3849,9 @@ def values(self) -> np.ndarray:
         Index.array : Reference to the underlying data.
         Index.to_numpy : A NumPy array representing the underlying data.
         """
-        return self._data.view(np.ndarray)
+        vals = self._data.view(np.ndarray)
+        vals.setflags(write=False)
+        return vals
 
     @cache_readonly
     @doc(IndexOpsMixin.array)
@@ -3858,7 +3860,7 @@ def array(self) -> ExtensionArray:
         if isinstance(array, np.ndarray):
             from pandas.core.arrays.numpy_ import PandasArray
 
-            array = PandasArray(array)
+            array = PandasArray(self.values)
         return array
 
     @property

pandas/tests/indexes/test_any_index.py

@@ -33,6 +33,20 @@ def test_mutability(index):
         index[0] = index[0]
 
 
+def test_values_mutability(index):
+    if not len(index):
+        return
+    with pytest.raises(ValueError):
+        index.values[0] = index[0]
+
+
+def test_array_mutability(index):
+    if not len(index):
+        return
+    with pytest.raises(ValueError):
+        index.array[0] = index[0]
+
+
 def test_wrong_number_names(index):
     names = index.nlevels * ["apple", "banana", "carrot"]
     with pytest.raises(ValueError, match="^Length"):