gh-39251: Require Python 3.11 or newer; remove outdated workarounds

    
<!-- ^ Please provide a concise and informative title. -->
<!-- ^ Don't put issue numbers in the title, do this in the PR
description below. -->
<!-- ^ For example, instead of "Fixes #12345" use "Introduce new method
to calculate 1 + 2". -->
<!-- v Describe your changes below in detail. -->
<!-- v Why is this change required? What problem does it solve? -->
<!-- v If this PR resolves an open issue, please link to it here. For
example, "Fixes #12345". -->

In line with Spec 0, we remove support for Python 3.9 and 3.10. Many
outdated patches/workarounds for these older (or even older) Python
versions are removed, but I cannot guarantee that I've found all
obsolete ones. Nothing in sage-the-distro is touched.

For next years cleaning job:
- Search for `3.11`, `311`, `PY_VERSION`, `PY_MINOR_VERSION` and
`sys.version_info`
- Change version in `pyproject.toml`


### 📝 Checklist

<!-- Put an `x` in all the boxes that apply. -->

- [ ] The title is concise and informative.
- [ ] The description explains in detail what this PR is about.
- [ ] I have linked a relevant issue or discussion.
- [ ] I have created tests covering the changes.
- [ ] I have updated the documentation and checked the documentation
preview.

### ⌛ Dependencies

<!-- List all open PRs that this PR logically depends on. For example,
-->
<!-- - #12345: short description why this is a dependency -->
<!-- - #34567: ... -->
    
URL: #39251
Reported by: Tobias Diez
Reviewer(s): Dima Pasechnik

.github/workflows/build.yml

@@ -15,7 +15,7 @@ on:
       platform:
         description: 'Platform'
         required: true
-        default: 'ubuntu-jammy-standard'
+        default: 'ubuntu-noble-standard'
       docker_tag:
         description: 'Docker tag'
         required: true
@@ -68,8 +68,8 @@ concurrency:
 
 env:
   # Adapted from docker.yml
-  TOX_ENV:                "docker-${{ github.event.inputs.platform || 'ubuntu-jammy-standard' }}-incremental"
-  BUILD_IMAGE:            "localhost:5000/${{ github.repository }}/sage-${{ github.event.inputs.platform || 'ubuntu-jammy-standard' }}-with-targets:ci"
+  TOX_ENV:                "docker-${{ github.event.inputs.platform || 'ubuntu-noble-standard' }}-incremental"
+  BUILD_IMAGE:            "localhost:5000/${{ github.repository }}/sage-${{ github.event.inputs.platform || 'ubuntu-noble-standard' }}-with-targets:ci"
   FROM_DOCKER_REPOSITORY: "ghcr.io/sagemath/sage/"
   FROM_DOCKER_TARGET:     "with-targets"
   FROM_DOCKER_TAG:        ${{ github.event.inputs.docker_tag || 'dev'}}

.github/workflows/dist.yml

@@ -216,7 +216,7 @@ jobs:
       #
       CIBW_ARCHS: ${{ matrix.arch }}
       # https://cibuildwheel.readthedocs.io/en/stable/options/#requires-python
-      CIBW_PROJECT_REQUIRES_PYTHON: ">=3.9, <3.13"
+      CIBW_PROJECT_REQUIRES_PYTHON: ">=3.11, <3.13"
       # Environment during wheel build
       CIBW_ENVIRONMENT: "PATH=$(pwd)/prefix/bin:$PATH CPATH=$(pwd)/prefix/include:$CPATH LIBRARY_PATH=$(pwd)/prefix/lib:$LIBRARY_PATH LD_LIBRARY_PATH=$(pwd)/prefix/lib:$LD_LIBRARY_PATH PKG_CONFIG_PATH=$(pwd)/prefix/share/pkgconfig:$PKG_CONFIG_PATH ACLOCAL_PATH=/usr/share/aclocal PIP_CONSTRAINT=$(pwd)/constraints.txt PIP_FIND_LINKS=file://$(pwd)/wheelhouse SAGE_NUM_THREADS=6"
       # Use 'build', not 'pip wheel'

.github/workflows/doc-build-pdf.yml

@@ -9,7 +9,7 @@ on:
       platform:
         description: 'Platform'
         required: true
-        default: 'ubuntu-jammy-standard'
+        default: 'ubuntu-noble-standard'
       docker_tag:
         description: 'Docker tag'
         required: true
@@ -22,8 +22,8 @@ concurrency:
 
 env:
   # Same as in build.yml
-  TOX_ENV:                "docker-${{ github.event.inputs.platform || 'ubuntu-jammy-standard' }}-incremental"
-  BUILD_IMAGE:            "localhost:5000/${{ github.repository }}/sage-${{ github.event.inputs.platform || 'ubuntu-jammy-standard' }}-with-targets:ci"
+  TOX_ENV:                "docker-${{ github.event.inputs.platform || 'ubuntu-noble-standard' }}-incremental"
+  BUILD_IMAGE:            "localhost:5000/${{ github.repository }}/sage-${{ github.event.inputs.platform || 'ubuntu-noble-standard' }}-with-targets:ci"
   FROM_DOCKER_REPOSITORY: "ghcr.io/sagemath/sage/"
   FROM_DOCKER_TARGET:     "with-targets"
   FROM_DOCKER_TAG:        ${{ github.event.inputs.docker_tag || 'dev'}}

.github/workflows/doc-build.yml

@@ -20,7 +20,7 @@ on:
       platform:
         description: 'Platform'
         required: true
-        default: 'ubuntu-jammy-standard'
+        default: 'ubuntu-noble-standard'
       docker_tag:
         description: 'Docker tag'
         required: true
@@ -33,8 +33,8 @@ concurrency:
 
 env:
   # Same as in build.yml
-  TOX_ENV:                "docker-${{ github.event.inputs.platform || 'ubuntu-jammy-standard' }}-incremental"
-  BUILD_IMAGE:            "localhost:5000/${{ github.repository }}/sage-${{ github.event.inputs.platform || 'ubuntu-jammy-standard' }}-with-targets:ci"
+  TOX_ENV:                "docker-${{ github.event.inputs.platform || 'ubuntu-noble-standard' }}-incremental"
+  BUILD_IMAGE:            "localhost:5000/${{ github.repository }}/sage-${{ github.event.inputs.platform || 'ubuntu-noble-standard' }}-with-targets:ci"
   FROM_DOCKER_REPOSITORY: "ghcr.io/sagemath/sage/"
   FROM_DOCKER_TARGET:     "with-targets"
   FROM_DOCKER_TAG:        ${{ github.event.inputs.docker_tag || 'dev'}}

.github/workflows/pyright.yml

@@ -18,7 +18,7 @@ concurrency:
 jobs:
   pyright:
     runs-on: ubuntu-latest
-    container: ghcr.io/sagemath/sage/sage-ubuntu-jammy-standard-with-targets:dev
+    container: ghcr.io/sagemath/sage/sage-ubuntu-noble-standard-with-targets:dev
     steps:
       - name: Checkout
         id: checkout

.gitignore

@@ -158,7 +158,6 @@ __pycache__/
 /src/sage/modular/arithgroup/farey_symbol.h
 # List of C and C++ files that are actual source files,
 # NOT generated by Cython. The same list appears in src/MANIFEST.in
-!/src/sage/cpython/debugimpl.c
 !/src/sage/graphs/base/boost_interface.cpp
 !/src/sage/graphs/cliquer/cl.c
 !/src/sage/graphs/graph_decompositions/sage_tdlib.cpp

README.md

@@ -222,7 +222,7 @@ in the Installation Guide.
       more details.
 
     - Python 3.4 or later, or Python 2.7, a full installation including
-      `urllib`; but ideally version 3.9.x, 3.10.x, 3.11.x, 3.12.x, which
+      `urllib`; but ideally version 3.11.x or later, which
       will avoid having to build Sage's own copy of Python 3.
       See [build/pkgs/python3/SPKG.rst](build/pkgs/python3/SPKG.rst)
       for more details.
@@ -557,11 +557,11 @@ SAGE_ROOT                 Root directory (create by git clone)
 │       │   ├── installed/
 │       │   │             Records of installed non-Python packages
 │       │   ├── scripts/  Scripts for uninstalling installed packages
-│       │   └── venv-python3.9  (SAGE_VENV)
+│       │   └── venv-python  (SAGE_VENV)
 │       │       │         Installation hierarchy (virtual environment)
 │       │       │         for Python packages
 │       │       ├── bin/  Executables and installed scripts
-│       │       ├── lib/python3.9/site-packages/
+│       │       ├── lib/python/site-packages/
 │       │       │         Python modules/packages are installed here
 │       │       └── var/lib/sage/
 │       │           └── wheels/

pyproject.toml

@@ -62,16 +62,14 @@ classifiers = [
     "Operating System :: POSIX",
     "Operating System :: MacOS :: MacOS X",
     "Programming Language :: Python :: 3 :: Only",
-    "Programming Language :: Python :: 3.9",
-    "Programming Language :: Python :: 3.10",
     "Programming Language :: Python :: 3.11",
     "Programming Language :: Python :: 3.12",
     "Programming Language :: Python :: 3.13",
     "Programming Language :: Python :: Implementation :: CPython",
     "Topic :: Scientific/Engineering :: Mathematics",
 ]
 urls = {Homepage = "https://www.sagemath.org"}
-requires-python = ">=3.9, <3.14"
+requires-python = ">=3.11, <3.14"
 
 [project.optional-dependencies]
 R = [

pyrightconfig.json

@@ -7,7 +7,7 @@
         "root": "src"
       }
     ],  
-    "pythonVersion": "3.9",
+    "pythonVersion": "3.11",
     "exclude": ["venv"],
     "venvPath": "./venv/",
     "venv": "./",

ruff.toml

@@ -1,7 +1,7 @@
 # https://docs.astral.sh/ruff/configuration/#config-file-discovery
 
-# Assume Python 3.9
-target-version = "py39"
+# Python 3.11 is the minimum supported version
+target-version = "py311"
 
 lint.select = [
     "E", # pycodestyle errors - https://docs.astral.sh/ruff/rules/#error-e

src/MANIFEST.in

@@ -23,7 +23,6 @@ global-exclude *.cpp
 # List of C and C++ files that are actual source files,
 # NOT generated by Cython. The same list appears in SAGE_ROOT/.gitignore
 #
-include sage/cpython/debugimpl.c
 include sage/graphs/base/boost_interface.cpp
 include sage/graphs/cliquer/cl.c
 include sage/libs/eclib/wrap.cpp

src/doc/en/developer/coding_in_python.rst

@@ -12,17 +12,14 @@ Sage.
 Python language standard
 ========================
 
-Sage library code needs to be compatible with all versions of Python
-that Sage supports.  The information regarding the supported versions
-can be found in the files ``build/pkgs/python3/spkg-configure.m4`` and
-``src/setup.cfg.m4``.
-
-Python 3.9 is the oldest supported version.  Hence,
-all language and library features that are available in Python 3.9 can
-be used; but features introduced in Python 3.10 cannot be used.  If a
-feature is deprecated in a newer supported version, it must be ensured
-that deprecation warnings issued by Python do not lead to failures in
-doctests.
+Sage follows the time window-based support policy
+`SPEC 0 — Minimum Supported Dependencies <https://scientific-python.org/specs/spec-0000/>`_
+for Python versions.
+The current minimum supported Python version can be found in the 
+``pyproject.toml`` file. Accordingly, only language and library features 
+available in this version can be used. If a feature is deprecated in a newer 
+supported version, it must be ensured that deprecation warnings issued by
+Python do not lead to failures in doctests.
 
 Some key language and library features have been backported to older Python versions
 using one of two mechanisms:
@@ -34,21 +31,9 @@ using one of two mechanisms:
   of annotations).  All Sage library code that uses type annotations
   should include this ``__future__`` import and follow PEP 563.
 
-- Backport packages
-
-  - `importlib_metadata <../reference/spkg/importlib_metadata>`_
-    (to be used in place of ``importlib.metadata``),
-  - `importlib_resources <../reference/spkg/importlib_resources>`_
-    (to be used in place of ``importlib.resources``),
-  - `typing_extensions <../reference/spkg/typing_extensions>`_
-    (to be used in place of ``typing``).
-
-  The Sage library declares these packages as dependencies and ensures that
-  versions that provide features of Python 3.11 are available.
-
-Meta :issue:`29756` keeps track of newer Python features and serves
-as a starting point for discussions on how to make use of them in the
-Sage library.
+- The `typing_extensions <../reference/spkg/typing_extensions>`_ package
+  is used to backport features from newer versions of the ``typing`` module.
+  The Sage library declares this package as a dependency.
 
 
 Design

src/doc/en/installation/conda.rst

@@ -50,7 +50,7 @@ Create a new conda environment containing SageMath, either with ``mamba`` or ``c
 
       $ conda create -n sage sage python=X
 
-where ``X`` is version of Python, e.g. ``3.9``.
+where ``X`` is version of Python, e.g. ``3.12``.
 
 To use Sage from there,
 
@@ -86,22 +86,22 @@ Here we assume that you are using a git checkout.
 
     .. code-block:: shell
 
-        $ mamba env create --file environment-3.11-linux.yml --name sage-dev
+        $ mamba env create --file environment-3.12-linux.yml --name sage-dev
         $ conda activate sage-dev
 
   .. tab:: conda
 
     .. code-block:: shell
 
-        $ conda env create --file environment-3.11-linux.yml --name sage-dev
+        $ conda env create --file environment-3.12-linux.yml --name sage-dev
         $ conda activate sage-dev
 
-  Alternatively, you can use ``environment-3.11-linux.yml`` or
-  ``environment-optional-3.11-linux.yml``, which will only install standard
+  Alternatively, you can use ``environment-3.12-linux.yml`` or
+  ``environment-optional-3.12-linux.yml``, which will only install standard
   (and optional) packages without any additional developer tools.
 
-  A different Python version can be selected by replacing ``3.11`` by ``3.9``
-  or ``3.10`` in these commands.
+  A different Python version can be selected by replacing ``3.12`` with the 
+  desired version.
 
 - Bootstrap the source tree and install the build prerequisites and the Sage library::
 
@@ -137,7 +137,7 @@ After editing any Cython files, rebuild the Sage library using::
 
 In order to update the conda environment later, you can run::
 
-  $ mamba env update --file environment-3.11-linux.yml --name sage-dev
+  $ mamba env update --file environment-3.12-linux.yml --name sage-dev
 
 To build the documentation, use::
 
@@ -156,5 +156,5 @@ To build the documentation, use::
 
   You can update the conda lock files by running
   ``.github/workflows/conda-lock-update.py`` or by running
-  ``conda-lock --platform linux-64 --filename environment-3.11-linux.yml --lockfile environment-3.11-linux.lock``
+  ``conda-lock --platform linux-64 --filename environment-3.12-linux.yml --lockfile environment-3.12-linux.lock``
   manually.

src/doc/en/installation/launching.rst

@@ -67,9 +67,8 @@ Sage uses the following environment variables when it runs:
 
 - See
   https://docs.python.org/3/using/cmdline.html#environment-variables
-  for more variables used by Python (not an exhaustive list). With
-  Python 3.11 or later, a brief summary can also be obtained by
-  running `python3 --help-env`.
+  for more variables used by Python (not an exhaustive list). 
+  A brief summary can also be obtained by running `python3 --help-env`.
 
 Using a Jupyter Notebook remotely
 ---------------------------------

src/sage/all__sagemath_repl.py

@@ -100,12 +100,6 @@
                         message=r"Pickle, copy, and deepcopy support will be "
                                 r"removed from itertools in Python 3.14.")
 
-# triggered in Python 3.9 on Redhat-based distributions
-# https://github.com/sagemath/sage/issues/37863
-# https://github.com/networkx/networkx/issues/7101
-warnings.filterwarnings('ignore', category=RuntimeWarning,
-                        message="networkx backend defined more than once: nx-loopback")
-
 from sage.all__sagemath_objects import *
 from sage.all__sagemath_environment import *
 

src/sage/cpython/atexit.pyx

@@ -148,8 +148,6 @@ from cpython.ref cimport PyObject
 # Implement "_atexit_callbacks()" for each supported python version
 cdef extern from *:
     """
-    #if PY_VERSION_HEX >= 0x030a0000
-    /********** Python 3.10 **********/
     #define Py_BUILD_CORE
     #undef _PyGC_FINALIZED
     #include "internal/pycore_interp.h"
@@ -163,29 +161,6 @@ cdef extern from *:
         struct atexit_state state = interp->atexit;
         return state.callbacks;
     }
-    #else
-    /********** Python < 3.10 **********/
-    /* Internal structures defined in the CPython source in
-     * Modules/atexitmodule.c and subject to (but unlikely to) change.  Watch
-     * https://bugs.python.org/issue32082 for a request to (eventually)
-     * re-expose more of the atexit module's internals to Python
-     * typedef struct
-     */
-    typedef struct {
-        PyObject *func;
-        PyObject *args;
-        PyObject *kwargs;
-    } atexit_callback;
-    typedef struct {
-        atexit_callback **atexit_callbacks;
-        int ncallbacks;
-        int callback_len;
-    } atexitmodule_state;
-    static atexit_callback ** _atexit_callbacks(PyObject *self) {
-        atexitmodule_state *state = PyModule_GetState(self);
-        return state->atexit_callbacks;
-    }
-    #endif
     """
     ctypedef struct atexit_callback:
         PyObject* func

src/sage/cpython/cython_metaclass.h

@@ -8,13 +8,6 @@
 *                  http://www.gnu.org/licenses/
 *****************************************************************************/
 
-/* Compatibility for python 3.8, can be removed later */
-#if PY_VERSION_HEX < 0x030900A4 && !defined(Py_SET_TYPE)
-static inline void _Py_SET_TYPE(PyObject *ob, PyTypeObject *type)
-{ ob->ob_type = type; }
-#define Py_SET_TYPE(ob, type) _Py_SET_TYPE((PyObject*)(ob), type)
-#endif
-
 /* Tuple (None, None, None), initialized as needed */
 static PyObject* NoneNoneNone;
 
@@ -52,15 +45,13 @@ static CYTHON_INLINE int Sage_PyType_Ready(PyTypeObject* t)
     if (r < 0)
         return r;
 
-#if PY_VERSION_HEX >= 0x03050000
     // Cython 3 sets Py_TPFLAGS_HEAPTYPE before calling PyType_Ready,
     // and resets just after the call. We need to reset it earlier,
     // since otherwise the call to metaclass.__init__ below may have
     // illegal memory accesses.
     // See also:
     // https://github.com/cython/cython/issues/3603
     t->tp_flags &= ~Py_TPFLAGS_HEAPTYPE;
-#endif
 
     /* Set or get metaclass (the type of t) */
     PyTypeObject* metaclass;

src/sage/cpython/debug.pyx

@@ -19,9 +19,6 @@ cdef extern from "Python.h":
     # Helper to get a pointer to an object's __dict__ slot, if any
     PyObject** _PyObject_GetDictPtr(obj)
 
-cdef extern from "debugimpl.c":
-    void _type_debug(PyTypeObject*)
-
 from sage.cpython.getattr cimport AttributeErrorMessage
 
 
@@ -303,5 +300,3 @@ def type_debug(cls):
     """
     if not isinstance(cls, type):
         raise TypeError(f"{cls!r} is not a type")
-
-    _type_debug(<PyTypeObject*>cls)