sagemathgh-35404: Drop support for Python 3.8

    
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### 📚 Description

In preparation for important package upgrades, we remove support for
Python v3.8. (Almost) all occurrences of "Python 3.8" are removed from
the codebase. There are still some comments left that essentially say
that in newer versions things can be simplified, but I didn't touch
those and leave them for follow-up PRs.

This will help with:
-  PRs that require Python 3.9 or above, such as
sagemath#34973 and
sagemath#35188.
- Upgrades of Python packages that have dropped support for Python 3.8
because they follow NEP 29 and have already released a new major version
that drops support according to the NEP 29 schedule.
  - NetworkX 3.2 (expected 2023-??; version 3.1 was released 2023-04,
see sagemath#35671)
  - sagemath#34816
  - sagemath#35703
  - See also sagemath#32074.

Test run: https://github.com/tobiasdiez/sage/actions/runs/4586981626

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- [x] 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.
- [x] I have updated the documentation accordingly.

### ⌛ Dependencies

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- sagemath#12345: short description why this is a dependency
- sagemath#34567: ...
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URL: sagemath#35404
Reported by: Tobias Diez
Reviewer(s): Dima Pasechnik, Matthias Köppe

.github/workflows/dist.yml

@@ -100,7 +100,7 @@ jobs:
       #
       CIBW_ARCHS: ${{ matrix.arch }}
       # https://cibuildwheel.readthedocs.io/en/stable/options/#requires-python
-      CIBW_PROJECT_REQUIRES_PYTHON: ">=3.8"
+      CIBW_PROJECT_REQUIRES_PYTHON: ">=3.9"
       # Environment during wheel build
       CIBW_ENVIRONMENT: "PATH=$(pwd)/local/bin:$PATH CPATH=$(pwd)/local/include:$CPATH LIBRARY_PATH=$(pwd)/local/lib:$LIBRARY_PATH PKG_CONFIG_PATH=$(pwd)/local/share/pkgconfig:$PKG_CONFIG_PATH ACLOCAL_PATH=/usr/share/aclocal"
       # Use 'build', not 'pip wheel'

.github/workflows/docker.yml

@@ -18,7 +18,6 @@ on:
         default: >-
           ["ubuntu-trusty-toolchain-gcc_9",
            "ubuntu-xenial-toolchain-gcc_9",
-           "ubuntu-bionic-gcc_8-python3.8",
            "ubuntu-focal",
            "ubuntu-jammy",
            "ubuntu-kinetic",
@@ -28,16 +27,13 @@ on:
            "debian-bullseye",
            "debian-bookworm",
            "debian-sid",
-           "linuxmint-19-gcc_8-python3.8",
-           "linuxmint-19.3-gcc_8-python3.8",
            "linuxmint-20.1",
            "linuxmint-20.2",
            "linuxmint-20.3",
            "linuxmint-21",
            "linuxmint-21.1",
            "linuxmint-21.2",
-           "fedora-29-python3.8",
-           "fedora-30-python3.8",
+           "fedora-30",
            "fedora-31",
            "fedora-32",
            "fedora-33",

.github/workflows/lint.yml

@@ -17,7 +17,7 @@ jobs:
     - name: Set up Python
       uses: actions/setup-python@v4
       with:
-        python-version: 3.8
+        python-version: 3.9
     - name: Install pycodestyle
       run: pip install tox pycodestyle
     - name: Lint using pycodestyle
@@ -31,7 +31,7 @@ jobs:
     - name: Set up Python
       uses: actions/setup-python@v4
       with:
-        python-version: 3.8
+        python-version: 3.9
     - name: Install relint
       run: pip install tox relint
     - name: Lint using relint
@@ -45,7 +45,7 @@ jobs:
     - name: Set up Python
       uses: actions/setup-python@v4
       with:
-        python-version: 3.8
+        python-version: 3.9
     - name: Install tox
       run: pip install tox
     - name: Lint using tox -e rst

README.md

@@ -201,7 +201,7 @@ in the Installation Guide.
       more details.
 
     - Python 3.4 or later, or Python 2.7, a full installation including
-      `urllib`; but ideally version 3.8.x, 3.9.x, or 3.10.x, which
+      `urllib`; but ideally version 3.9.x, 3.10.x, or 3.11.x, 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.

build/pkgs/python3/SPKG.rst

@@ -8,7 +8,7 @@ By default, Sage will try to use system's ``python3`` to set up a virtual
 environment, a.k.a. `venv <https://docs.python.org/3.10/library/venv.html>`_
 rather than building a Python 3 installation from scratch.
 
-Sage will accept versions 3.8.x to 3.10.x.
+Sage will accept versions 3.9.x to 3.10.x.
 
 You can also use ``--with-python=/path/to/python3_binary`` to tell Sage to use
 ``/path/to/python3_binary`` to set up the venv. Note that setting up the venv requires

build/pkgs/python3/spkg-configure.m4

@@ -1,6 +1,6 @@
 SAGE_SPKG_CONFIGURE([python3], [
-   m4_pushdef([MIN_VERSION],               [3.8.0])
-   m4_pushdef([MIN_NONDEPRECATED_VERSION], [3.8.0])
+   m4_pushdef([MIN_VERSION],               [3.9.0])
+   m4_pushdef([MIN_NONDEPRECATED_VERSION], [3.9.0])
    m4_pushdef([LT_STABLE_VERSION],         [3.12.0])
    m4_pushdef([LT_VERSION],                [3.12.0])
    AC_ARG_WITH([python],

build/pkgs/tzlocal/dependencies

@@ -1,4 +1,4 @@
-$(PYTHON) backports_zoneinfo pytz_deprecation_shim | $(PYTHON_TOOLCHAIN)
+$(PYTHON) pytz_deprecation_shim | $(PYTHON_TOOLCHAIN)
 
 ----------
 All lines of this file are ignored except the first.

m4/setup_cfg_metadata.m4

@@ -13,7 +13,6 @@ classifiers =
     Operating System :: POSIX
     Operating System :: MacOS :: MacOS X
     Programming Language :: Python :: 3 :: Only
-    Programming Language :: Python :: 3.8
     Programming Language :: Python :: 3.9
     Programming Language :: Python :: 3.10
     Programming Language :: Python :: 3.11

pkgs/sage-docbuild/setup.cfg

@@ -17,7 +17,6 @@ classifiers =
     Operating System :: POSIX
     Operating System :: MacOS :: MacOS X
     Programming Language :: Python :: 3 :: Only
-    Programming Language :: Python :: 3.8
     Programming Language :: Python :: 3.9
     Programming Language :: Python :: 3.10
     Programming Language :: Python :: 3.11

pkgs/sage-setup/setup.cfg

@@ -32,7 +32,7 @@ packages =
     sage_setup.autogen.interpreters.specs
     sage_setup.command
 
-python_requires = >=3.8, <3.12
+python_requires = >=3.9, <3.12
 
 install_requires =
     pkgconfig

pkgs/sagemath-categories/setup.cfg.m4

@@ -8,7 +8,7 @@ long_description_content_type = text/x-rst
 include(`setup_cfg_metadata.m4')dnl'
 
 [options]
-python_requires = >=3.8, <3.12
+python_requires = >=3.9, <3.12
 install_requires =
     SPKG_INSTALL_REQUIRES_sagemath_objects
 

pkgs/sagemath-environment/setup.cfg.m4

@@ -8,7 +8,7 @@ long_description_content_type = text/x-rst
 include(`setup_cfg_metadata.m4')dnl'
 
 [options]
-python_requires = >=3.8, <3.12
+python_requires = >=3.9, <3.12
 install_requires =
 
 py_modules =

pkgs/sagemath-objects/setup.cfg.m4

@@ -9,7 +9,7 @@ include(`setup_cfg_metadata.m4')dnl'
 
 [options]
 include(`sage_spkg_versions.m4')dnl'
-python_requires = >=3.8, <3.12
+python_requires = >=3.9, <3.12
 install_requires =
     SPKG_INSTALL_REQUIRES_gmpy2
     SPKG_INSTALL_REQUIRES_cysignals

pkgs/sagemath-repl/setup.cfg.m4

@@ -8,7 +8,7 @@ long_description_content_type = text/x-rst
 include(`setup_cfg_metadata.m4')dnl'
 
 [options]
-python_requires = >=3.8, <3.12
+python_requires = >=3.9, <3.12
 install_requires =
     SPKG_INSTALL_REQUIRES_sagemath_objects
     SPKG_INSTALL_REQUIRES_sagemath_environment

pyrightconfig.json

@@ -7,7 +7,7 @@
         "root": "src"
       }
     ],  
-    "pythonVersion": "3.8",
+    "pythonVersion": "3.9",
     "exclude": ["venv"],
     "venvPath": "./venv/",
     "venv": "./",

src/doc/en/developer/coding_basics.rst

@@ -945,7 +945,7 @@ written.
   for both examples.
 
 - **Preparsing:** As in Sage's console, `4/3` returns `4/3` and not
-  `1.3333333333333333` as in Python 3.8. Testing occurs with full Sage
+  `1.3333333333333333` as in Python. Testing occurs with full Sage
   preparsing of input within the standard Sage shell environment, as
   described in :ref:`section-preparsing`.
 

src/doc/en/developer/coding_in_python.rst

@@ -16,18 +16,18 @@ 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``.
 
-As of Sage 9.7, Python 3.8 is the oldest supported version.  Hence,
-all language and library features that are available in Python 3.8 can
-be used; but features introduced in Python 3.9 cannot be used.  If a
+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.
 
-Some key language and library features have been backported to Python 3.8
+Some key language and library features have been backported to older Python versions
 using one of two mechanisms:
 
 - ``from __future__ import annotations`` (see Python reference for
-  `__future__ <https://docs.python.org/3.8/library/__future__.html>`_)
+  `__future__ <https://docs.python.org/3/library/__future__.html>`_)
   modernizes type annotations according to `PEP 563
   <https://www.python.org/dev/peps/pep-0563>`_ (Postponed evaluation
   of annotations).  All Sage library code that uses type annotations

src/sage/algebras/fusion_rings/f_matrix.py

@@ -1229,11 +1229,6 @@ def start_worker_pool(self, processes=None):
         :meth:`shutdown_worker_pool` to close the pool and properly dispose
         of shared memory resources.
 
-        .. NOTE::
-
-            Python 3.8+ is required, since the ``multiprocessing.shared_memory``
-            module must be imported.
-
         INPUT:
 
         - ``processes`` -- an integer indicating the number of workers

src/sage/algebras/fusion_rings/fusion_ring.py

@@ -1289,7 +1289,7 @@ def get_braid_generators(self,
           we don't run the solver again.
         - ``use_mp`` -- (default: ``True``) a boolean indicating whether
           to use multiprocessing to speed up the computation; this is
-          highly recommended. Python 3.8+ is required.
+          highly recommended.
         - ``verbose`` -- (default: ``True``) boolean indicating whether
           to be verbose with the computation
 

src/sage/algebras/fusion_rings/shm_managers.pyx

@@ -55,8 +55,7 @@ cdef class KSHandler:
     - ``n_slots`` -- the total number of F-symbols
     - ``field`` -- F-matrix's base cyclotomic field
     - ``use_mp`` -- a boolean indicating whether to construct a shared
-      memory block to back ``self``. Requires Python 3.8+, since we
-      must import the ``multiprocessing.shared_memory`` module.
+      memory block to back ``self``.
     - ``init_data`` -- a dictionary or :class:`KSHandler` object containing
       known squares for initialization, e.g., from a solver checkpoint
     - ``name`` -- the name of a shared memory object (used by child processes
@@ -391,9 +390,6 @@ cdef class FvarsHandler:
     ``name`` attribute. Children processes use the ``name`` attribute,
     accessed via ``self.shm.name`` to attach to the shared memory block.
 
-    Multiprocessing requires Python 3.8+, since we must import the
-    ``multiprocessing.shared_memory`` module.
-
     INPUT:
 
     - ``n_slots`` -- number of generators of the underlying polynomial ring

src/setup.cfg.m4

@@ -9,7 +9,7 @@ license_files = LICENSE.txt
 include(`setup_cfg_metadata.m4')dnl'
 
 [options]
-python_requires = >=3.8, <3.12
+python_requires = >=3.9, <3.12
 install_requires =
     SPKG_INSTALL_REQUIRES_sage_conf
     SPKG_INSTALL_REQUIRES_six

tox.ini

@@ -527,24 +527,23 @@ setenv =
     # to "--with-system-python3=force" as originally proposed in #32060
                                                                  PYTHON_MAJOR=3
                                                                    PYTHON_MINOR=10
-    python3.8:                                                     PYTHON_MINOR=8
     python3.9:                                                     PYTHON_MINOR=9
     python3.10:                                                    PYTHON_MINOR=10
     python3.11:                                                    PYTHON_MINOR=11
     python3.12:                                                    PYTHON_MINOR=12
                                                                      CONFIG_CONFIGURE_ARGS_1=--with-system-python3=yes
     python3_spkg:                                                    CONFIG_CONFIGURE_ARGS_1=--without-system-python3
-    python3.8,python3.9,python3.10,python3.11,python3.12:            CONFIG_CONFIGURE_ARGS_1=--with-system-python3=force --with-python=python{env:PYTHON_MAJOR}.{env:PYTHON_MINOR}
-    python3.8,python3.9,python3.10,python3.11,python3.12:              EXTRA_SAGE_PACKAGES_5=_python{env:PYTHON_MAJOR}.{env:PYTHON_MINOR} _bootstrap liblzma bzip2 libffi libpng zlib
+    python3.9,python3.10,python3.11,python3.12:                      CONFIG_CONFIGURE_ARGS_1=--with-system-python3=force --with-python=python{env:PYTHON_MAJOR}.{env:PYTHON_MINOR}
+    python3.9,python3.10,python3.11,python3.12:                        EXTRA_SAGE_PACKAGES_5=_python{env:PYTHON_MAJOR}.{env:PYTHON_MINOR} _bootstrap liblzma bzip2 libffi libpng zlib
     macos-python3_xcode:                                             CONFIG_CONFIGURE_ARGS_1=--with-system-python3=force --with-python=/usr/bin/python3
     macos-{python3_xcode,nohomebrew}-{python3.8}:                    CONFIG_CONFIGURE_ARGS_1=--with-system-python3=force --with-python=/Library/Developer/CommandLineTools/Library/Frameworks/Python3.framework/Versions/{env:PYTHON_MAJOR}.{env:PYTHON_MINOR}/bin/python3
     # Homebrew keg installs
-    homebrew-{python3.8,python3.9,python3.10,python3.11,python3.12}: CONFIG_CONFIGURE_ARGS_1=--with-system-python3=force --with-python={env:HOMEBREW}/opt/python@{env:PYTHON_MAJOR}.{env:PYTHON_MINOR}/bin/python3
+    homebrew-{python3.9,python3.10,python3.11,python3.12}: CONFIG_CONFIGURE_ARGS_1=--with-system-python3=force --with-python={env:HOMEBREW}/opt/python@{env:PYTHON_MAJOR}.{env:PYTHON_MINOR}/bin/python3
     # Installers from https://www.python.org/downloads/macos/ (must manually download and install)
     macos-python3_pythonorg:                                         CONFIG_CONFIGURE_ARGS_1=--with-system-python3=force --with-python=/Library/Frameworks/Python.framework/Versions/{env:PYTHON_MAJOR}.{env:PYTHON_MINOR}/bin/python3
     # https://github.com/pypa/manylinux
     manylinux-standard:                                              CONFIG_CONFIGURE_ARGS_1=--with-system-python3=force --with-python=/opt/python/cp{env:PYTHON_MAJOR}{env:PYTHON_MINOR}-cp{env:PYTHON_MAJOR}{env:PYTHON_MINOR}/bin/python3
-    manylinux-{python3.8,python3.9,python3.10,python3.11,python3.12}:  EXTRA_SAGE_PACKAGES_5=_bootstrap liblzma bzip2 libffi libpng
+    manylinux-{python3.9,python3.10,python3.11,python3.12}:            EXTRA_SAGE_PACKAGES_5=_bootstrap liblzma bzip2 libffi libpng
     conda:                                                           CONFIG_CONFIGURE_ARGS_1=--with-system-python3=force --with-python=python3
     #
     #  - toolchain