deps!(python): drop Python 3.9 support

Author: XuehaiPan

.github/workflows/build.yml

@@ -77,7 +77,7 @@ jobs:
       - name: Set up Python
         uses: actions/setup-python@v6
         with:
-          python-version: "3.9 - 3.14"
+          python-version: "3.10 - 3.14"
           update-environment: true
 
       - name: Upgrade pip
@@ -146,7 +146,6 @@ jobs:
           - { runner: windows-latest, platform: windows, archs: "auto32" }
           - { runner: windows-11-arm, platform: windows, archs: "ARM64" }
         python-version:
-          - "3.9"
           - "3.10"
           - "3.11"
           - "3.12"
@@ -157,8 +156,6 @@ jobs:
           - "pypy-3.11"
         exclude:
           # Exclude unsupported Python versions
-          - python-version: "3.9"
-            target: { archs: "ARM64" }
           - python-version: "3.10"
             target: { archs: "ARM64" }
           - python-version: "pypy-3.11"
@@ -387,7 +384,7 @@ jobs:
         if: startsWith(github.ref, 'refs/tags/')
         uses: actions/setup-python@v6
         with:
-          python-version: "3.9 - 3.14"
+          python-version: "3.10 - 3.14"
           update-environment: true
 
       - name: Upgrade pip

.github/workflows/tests-with-pydebug.yml

@@ -67,16 +67,13 @@ jobs:
       matrix:
         runner: [ubuntu-latest, macos-latest, windows-latest]
         python-version:
-          - "3.9"
           - "3.10"
           - "3.11"
           - "3.12"
           - "3.13"
           - "3.14"
         python-abiflags: ["d", "td"]
         exclude:
-          - python-version: "3.9"
-            python-abiflags: "td"
           - python-version: "3.10"
             python-abiflags: "td"
           - python-version: "3.11"

.github/workflows/tests.yml

@@ -66,7 +66,6 @@ jobs:
       matrix:
         runner: [ubuntu-latest, macos-latest, windows-latest]
         python-version:
-          - "3.9"
           - "3.10"
           - "3.11"
           - "3.12"

CONTRIBUTING.md

@@ -88,13 +88,13 @@ python3 -m cibuildwheel --platform=linux --output-dir=wheelhouse --config-file=p
 It will build wheel binaries for all supported CPython versions. The outputs will be placed in the `wheelhouse` directory.
 
 To build a wheel for a specific CPython version, you can use the [`CIBW_BUILD`](https://cibuildwheel.readthedocs.io/en/stable/options/#build-skip) environment variable.
-For example, the following command will build a wheel for Python 3.9:
+For example, the following command will build a wheel for Python 3.10:
 
 ```bash
-CIBW_BUILD="cp39*manylinux*" python3 -m cibuildwheel --platform=linux --output-dir=wheelhouse --config-file=pyproject.toml
+CIBW_BUILD="cp310*manylinux*" python3 -m cibuildwheel --platform=linux --output-dir=wheelhouse --config-file=pyproject.toml
 ```
 
-You can change `cp39*` to `cp312*` to build for Python 3.12. See <https://cibuildwheel.readthedocs.io/en/stable/options> for more options.
+You can change `cp310*` to `cp312*` to build for Python 3.12. See <https://cibuildwheel.readthedocs.io/en/stable/options> for more options.
 
 ## Documentation
 

README.md

@@ -2,7 +2,7 @@
 
 # OpTree
 
-![Python 3.9+](https://img.shields.io/badge/Python-3.9%2B-brightgreen)
+![Python 3.10+](https://img.shields.io/badge/Python-3.10%2B-brightgreen)
 [![PyPI](https://img.shields.io/pypi/v/optree?logo=pypi)](https://pypi.org/project/optree)
 ![GitHub Workflow Status](https://img.shields.io/github/actions/workflow/status/metaopt/optree/build.yml?label=build&logo=github)
 ![GitHub Workflow Status](https://img.shields.io/github/actions/workflow/status/metaopt/optree/tests.yml?label=tests&logo=github)
@@ -71,7 +71,7 @@ export pybind11_DIR="/path/to/custom/pybind11"
 pip3 install .
 ```
 
-Compiling from the source requires Python 3.9+, a compiler (`gcc` / `clang` / `icc` / `cl.exe`) that supports C++20 and a `cmake` installation.
+Compiling from the source requires Python 3.10+, a compiler (`gcc` / `clang` / `icc` / `cl.exe`) that supports C++20 and a `cmake` installation.
 
 --------------------------------------------------------------------------------
 

docs/source/conf.py

@@ -228,8 +228,8 @@ def typehints_formatter(annotation, config=None):
     import optree
 
     if (
-        isinstance(annotation, type(typing.Union[int, str]))
-        and typing.get_origin(annotation) is typing.Union
+        isinstance(annotation, type(int | str))
+        and typing.get_origin(annotation) is type(int | str)
         and annotation in optree.PyTree.__instances__
     ):
         param, name = optree.PyTree.__instances__[annotation]

include/optree/pymacros.h

@@ -23,8 +23,8 @@ limitations under the License.
 
 #include <pybind11/pybind11.h>
 
-#if !(defined(PY_VERSION_HEX) && PY_VERSION_HEX >= 0x03090000)  // Python 3.9
-#    error "Python 3.9 or newer is required."
+#if !(defined(PY_VERSION_HEX) && PY_VERSION_HEX >= 0x030A0000)  // Python 3.10
+#    error "Python 3.10 or newer is required."
 #endif
 
 #if !(defined(PYBIND11_VERSION_HEX) && PYBIND11_VERSION_HEX >= 0x020C00F0)  // pybind11 2.12.0

optree/accessors.py

@@ -17,7 +17,6 @@
 from __future__ import annotations
 
 import dataclasses
-import sys
 from collections.abc import Iterable, Mapping, Sequence
 from typing import TYPE_CHECKING, Any, ClassVar, Generic, Literal, TypeVar, overload
 from typing_extensions import Self  # Python 3.11+
@@ -47,10 +46,7 @@
 ]
 
 
-SLOTS = {'slots': True} if sys.version_info >= (3, 10) else {}  # Python 3.10+
-
-
-@dataclasses.dataclass(init=True, repr=False, eq=False, frozen=True, **SLOTS)
+@dataclasses.dataclass(init=True, repr=False, eq=False, frozen=True, slots=True)
 class PyTreeEntry:
     """Base class for path entries."""
 
@@ -122,9 +118,6 @@ def codify(self, /, node: str = '') -> str:
         return f'{node}[<flat index {self.entry!r}>]'  # should be overridden
 
 
-del SLOTS
-
-
 _T = TypeVar('_T')
 _T_co = TypeVar('_T_co', covariant=True)
 _KT_co = TypeVar('_KT_co', covariant=True)
@@ -134,8 +127,6 @@ def codify(self, /, node: str = '') -> str:
 class AutoEntry(PyTreeEntry):
     """A generic path entry class that determines the entry type on creation automatically."""
 
-    __slots__: ClassVar[tuple[()]] = ()
-
     def __new__(  # type: ignore[misc]
         cls,
         /,
@@ -184,8 +175,6 @@ def __new__(  # type: ignore[misc]
 class GetItemEntry(PyTreeEntry):
     """A generic path entry class for nodes that access their children by :meth:`__getitem__`."""
 
-    __slots__: ClassVar[tuple[()]] = ()
-
     def __call__(self, obj: Any, /) -> Any:
         """Get the child object."""
         return obj[self.entry]
@@ -198,8 +187,6 @@ def codify(self, /, node: str = '') -> str:
 class GetAttrEntry(PyTreeEntry):
     """A generic path entry class for nodes that access their children by :meth:`__getattr__`."""
 
-    __slots__: ClassVar[tuple[()]] = ()
-
     entry: str
 
     @property
@@ -219,14 +206,10 @@ def codify(self, /, node: str = '') -> str:
 class FlattenedEntry(PyTreeEntry):  # pylint: disable=too-few-public-methods
     """A fallback path entry class for flattened objects."""
 
-    __slots__: ClassVar[tuple[()]] = ()
-
 
 class SequenceEntry(GetItemEntry, Generic[_T_co]):
     """A path entry class for sequences."""
 
-    __slots__: ClassVar[tuple[()]] = ()
-
     entry: int
     type: builtins.type[Sequence[_T_co]]
 
@@ -247,8 +230,6 @@ def __repr__(self, /) -> str:
 class MappingEntry(GetItemEntry, Generic[_KT_co, _VT_co]):
     """A path entry class for mappings."""
 
-    __slots__: ClassVar[tuple[()]] = ()
-
     entry: _KT_co
     type: builtins.type[Mapping[_KT_co, _VT_co]]
 
@@ -269,8 +250,6 @@ def __repr__(self, /) -> str:
 class NamedTupleEntry(SequenceEntry[_T]):
     """A path entry class for namedtuple objects."""
 
-    __slots__: ClassVar[tuple[()]] = ()
-
     entry: int
     type: builtins.type[NamedTuple[_T]]  # type: ignore[type-arg]
     kind: Literal[PyTreeKind.NAMEDTUPLE]
@@ -299,8 +278,6 @@ def codify(self, /, node: str = '') -> str:
 class StructSequenceEntry(SequenceEntry[_T]):
     """A path entry class for PyStructSequence objects."""
 
-    __slots__: ClassVar[tuple[()]] = ()
-
     entry: int
     type: builtins.type[StructSequence[_T]]
     kind: Literal[PyTreeKind.STRUCTSEQUENCE]
@@ -329,8 +306,6 @@ def codify(self, /, node: str = '') -> str:
 class DataclassEntry(GetAttrEntry):
     """A path entry class for dataclasses."""
 
-    __slots__: ClassVar[tuple[()]] = ()
-
     entry: str | int  # type: ignore[assignment]
 
     @property