Drop support for python<3.9.

PiperOrigin-RevId: 584861096

Author: hbq1

.github/workflows/ci.yml

@@ -13,12 +13,12 @@ jobs:
 
     strategy:
       matrix:
-        python-version: ["3.7", "3.8", "3.9"]
+        python-version: ["3.10", "3.11", "3.12"]
         os: [ubuntu-latest]
 
     steps:
-      - uses: "actions/checkout@v2"
-      - uses: "actions/setup-python@v1"
+      - uses: "actions/checkout@v4"
+      - uses: "actions/setup-python@v4"
         with:
             python-version: "${{ matrix.python-version }}"
       - name: Run CI tests

setup.py

@@ -58,7 +58,7 @@ def _parse_requirements(path):
     tests_require=_parse_requirements(
         os.path.join(_CURRENT_DIR, 'requirements', 'requirements-test.txt')),
     zip_safe=False,  # Required for full installation.
-    python_requires='>=3.7',
+    python_requires='>=3.9',
     classifiers=[
         'Development Status :: 4 - Beta',
         'Intended Audience :: Science/Research',

test.sh

@@ -25,7 +25,7 @@ python --version
 
 # Install dependencies.
 pip install --upgrade pip setuptools wheel
-pip install flake8 pytest-xdist pytype pylint pylint-exit
+pip install flake8 pytest-xdist pylint pylint-exit
 pip install -r requirements/requirements.txt
 pip install -r requirements/requirements-test.txt
 
@@ -46,7 +46,13 @@ pip wheel --verbose --no-deps --no-clean dist/mctx*.tar.gz
 pip install mctx*.whl
 
 # Check types with pytype.
-pytype `find mctx/_src/ -name "*py" | xargs` -k
+# Note: pytype does not support 3.12 as of 23.11.23
+# See https://github.com/google/pytype/issues/1308
+if [ `python -c 'import sys; print(sys.version_info.minor)'` -lt 12 ];
+then
+  pip install pytype
+  pytype `find mctx/_src/ -name "*py" | xargs` -k
+fi;
 
 # Run tests using pytest.
 # Change directory to avoid importing the package from repo root.