fix(db-dtypes): Drop support for Python <= 3.9 (#16966)

This PR updates \`db-dtypes\` to establish Python 3.10 as the minimum
supported version, dropping support for Python 3.7, 3.8, and 3.9.

### Changes

* Configuration: Updated setup.py metadata and python_requires to
>=3.10.
* Nox: Updated noxfile.py sessions and deleted constraints-3.9.txt.
* Documentation: Updated README.rst and CONTRIBUTING.rst (and synced to
docs/README.rst!).
* Removed extract_runtime_version and its helper file from db_dtypes
* Updated the tests to mock sys.version_info correctly.

Fixes internal issue: http://b/482126936 🦕

Author: chalmerlowe

packages/db-dtypes/CONTRIBUTING.rst

@@ -22,7 +22,7 @@ In order to add a feature:
   documentation.
 
 - The feature must work fully on the following CPython versions:
-  3.9, 3.10, 3.11, 3.12, 3.13 and 3.14 on both UNIX and Windows.
+  3.10, 3.11, 3.12, 3.13 and 3.14 on both UNIX and Windows.
 
 - The feature must not add unnecessary dependencies (where
   "unnecessary" is of course subjective, but new dependencies should
@@ -143,13 +143,12 @@ Running System Tests
    $ nox -s system
 
    # Run a single system test
-   $ nox -s system-3.9 -- -k <name of test>
+   $ nox -s system-3.12 -- -k <name of test>
 
 
   .. note::
 
-      System tests are only configured to run under Python 3.9.
-      For expediency, we do not run them in older versions of Python 3.
+      System tests are only configured to run under Python 3.12.
 
   This alone will not run the tests. You'll need to change some local
   auth settings and change some configuration in your project to
@@ -198,14 +197,12 @@ Supported Python Versions
 
 We support:
 
--  `Python 3.9`_
 -  `Python 3.10`_
 -  `Python 3.11`_
 -  `Python 3.12`_
 -  `Python 3.13`_
 -  `Python 3.14`_
 
-.. _Python 3.9: https://docs.python.org/3.9/
 .. _Python 3.10: https://docs.python.org/3.10/
 .. _Python 3.11: https://docs.python.org/3.11/
 .. _Python 3.12: https://docs.python.org/3.12/
@@ -218,17 +215,7 @@ Supported versions can be found in our ``noxfile.py`` `config`_.
 .. _config: https://github.com/googleapis/google-cloud-python/blob/main/packages/db-dtypes/noxfile.py
 
 
-We also explicitly decided to support Python 3 beginning with version 3.9.
-Reasons for this include:
 
--  Encouraging use of newest versions of Python 3
--  Taking the lead of `prominent`_ open-source `projects`_
--  `Unicode literal support`_ which allows for a cleaner codebase that
-   works in both Python 2 and Python 3
-
-.. _prominent: https://docs.djangoproject.com/en/1.9/faq/install/#what-python-version-can-i-use-with-django
-.. _projects: http://flask.pocoo.org/docs/0.10/python3/
-.. _Unicode literal support: https://www.python.org/dev/peps/pep-0414/
 
 **********
 Versioning

packages/db-dtypes/README.rst

@@ -34,11 +34,11 @@ dependencies.
 
 Supported Python Versions
 ^^^^^^^^^^^^^^^^^^^^^^^^^
-Python >= 3.9
+Python >= 3.10
 
 Unsupported Python Versions
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^
-Python <= 3.8.
+Python <= 3.9
 
 
 Mac/Linux

packages/db-dtypes/db_dtypes/__init__.py

@@ -30,7 +30,6 @@
 from db_dtypes import core
 from db_dtypes.json import JSONArray, JSONArrowType, JSONDtype  # noqa: F401
 
-from . import _versions_helpers
 
 date_dtype_name = "dbdate"
 time_dtype_name = "dbtime"
@@ -341,12 +340,13 @@ def __sub__(self, other):
 
 def _check_python_version():
     """Checks the runtime Python version and issues a warning if needed."""
-    sys_major, sys_minor, sys_micro = _versions_helpers.extract_runtime_version()
-    if sys_major == 3 and sys_minor in (7, 8):
+    import sys
+
+    if sys.version_info < (3, 10):
         warnings.warn(
             "The python-bigquery library as well as the python-db-dtypes-pandas library no "
-            "longer supports Python 3.7 and Python 3.8. "
-            f"Your Python version is {sys_major}.{sys_minor}.{sys_micro}. We "
+            "longer supports Python 3.7, 3.8, and 3.9. "
+            f"Your Python version is {sys.version_info.major}.{sys.version_info.minor}.{sys.version_info.micro}. We "
             "recommend that you update soon to ensure ongoing support. For "
             "more details, see: [Google Cloud Client Libraries Supported Python Versions policy](https://cloud.google.com/python/docs/supported-python-versions)",
             FutureWarning,

packages/db-dtypes/db_dtypes/_versions_helpers.py

@@ -34,11 +34,11 @@ dependencies.
 
 Supported Python Versions
 ^^^^^^^^^^^^^^^^^^^^^^^^^
-Python >= 3.9
+Python >= 3.10
 
 Unsupported Python Versions
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^
-Python <= 3.8.
+Python <= 3.9
 
 
 Mac/Linux

packages/db-dtypes/docs/README.rst

@@ -37,7 +37,6 @@
 LINT_PYTHON_VERSION = "3.10"
 
 UNIT_TEST_PYTHON_VERSIONS: List[str] = [
-    "3.9",
     "3.10",
     "3.11",
     "3.12",
@@ -58,7 +57,7 @@
 UNIT_TEST_EXTRAS: List[str] = []
 UNIT_TEST_EXTRAS_BY_PYTHON: Dict[str, List[str]] = {}
 
-SYSTEM_TEST_PYTHON_VERSIONS: List[str] = ["3.9"]
+SYSTEM_TEST_PYTHON_VERSIONS: List[str] = ["3.12"]
 SYSTEM_TEST_STANDARD_DEPENDENCIES: List[str] = [
     "mock",
     "pytest",

packages/db-dtypes/noxfile.py

@@ -64,7 +64,6 @@ def readme():
         "License :: OSI Approved :: Apache Software License",
         "Programming Language :: Python",
         "Programming Language :: Python :: 3",
-        "Programming Language :: Python :: 3.9",
         "Programming Language :: Python :: 3.10",
         "Programming Language :: Python :: 3.11",
         "Programming Language :: Python :: 3.12",
@@ -75,6 +74,6 @@ def readme():
     ],
     platforms="Posix; MacOS X; Windows",
     install_requires=dependencies,
-    python_requires=">=3.9",
+    python_requires=">=3.10",
     tests_require=["pytest"],
 )

packages/db-dtypes/setup.py

@@ -0,0 +1,10 @@
+# This constraints file is used to check that lower bounds
+# are correct in setup.py
+# List all library dependencies and extras in this file,
+# pinning their versions to their lower bounds.
+# For example, if setup.py has "google-cloud-foo >= 1.14.0, < 2.0.0",
+# then this file should have google-cloud-foo==1.14.0
+numpy==1.24.0
+packaging==24.2.0
+pandas==1.5.3
+pyarrow==13.0.0

packages/db-dtypes/testing/constraints-3.10.txt

@@ -12,16 +12,17 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from collections import namedtuple
 from unittest import mock
 
 import pytest
 
 # Module paths used for mocking
 MODULE_PATH = "db_dtypes"
-HELPER_MODULE_PATH = f"{MODULE_PATH}._versions_helpers"
-MOCK_EXTRACT_VERSION = f"{HELPER_MODULE_PATH}.extract_runtime_version"
 MOCK_WARN = "warnings.warn"  # Target the standard warnings module
 
+VersionInfo = namedtuple("VersionInfo", ["major", "minor", "micro"])
+
 
 @pytest.mark.parametrize(
     "mock_version_tuple, version_str",
@@ -30,17 +31,20 @@
         ((3, 7, 0), "3.7.0"),
         ((3, 8, 5), "3.8.5"),
         ((3, 8, 12), "3.8.12"),
+        ((3, 9, 5), "3.9.5"),
     ],
 )
 def test_check_python_version_warns_on_unsupported(mock_version_tuple, version_str):
     """
-    Test that _check_python_version issues a FutureWarning for Python 3.7/3.8.
+    Test that _check_python_version issues a FutureWarning for Python 3.7/3.8/3.9.
     """
 
     from db_dtypes import _check_python_version
 
-    # Mock the helper function it calls and the warnings.warn function
-    with mock.patch(MOCK_EXTRACT_VERSION, return_value=mock_version_tuple), mock.patch(
+    mock_version = VersionInfo(*mock_version_tuple)
+
+    # Mock sys.version_info and warnings.warn
+    with mock.patch("sys.version_info", new=mock_version), mock.patch(
         MOCK_WARN
     ) as mock_warn_call:
         _check_python_version()  # Call the function
@@ -55,17 +59,18 @@ def test_check_python_version_warns_on_unsupported(mock_version_tuple, version_s
         warning_category = args[1] if len(args) > 1 else kwargs.get("category")
 
         # Verify message content and category
-        assert "longer supports Python 3.7 and Python 3.8" in warning_message
+        assert "longer supports Python 3.7, 3.8, and 3.9" in warning_message
         assert warning_category == FutureWarning
 
 
 @pytest.mark.parametrize(
     "mock_version_tuple",
     [
-        (3, 9, 1),
         (3, 10, 0),
         (3, 11, 2),
         (3, 12, 0),
+        (3, 13, 0),
+        (3, 14, 0),
     ],
 )
 def test_check_python_version_does_not_warn_on_supported(mock_version_tuple):
@@ -75,8 +80,10 @@ def test_check_python_version_does_not_warn_on_supported(mock_version_tuple):
 
     from db_dtypes import _check_python_version
 
-    # Mock the helper function it calls and the warnings.warn function
-    with mock.patch(MOCK_EXTRACT_VERSION, return_value=mock_version_tuple), mock.patch(
+    mock_version = VersionInfo(*mock_version_tuple)
+
+    # Mock sys.version_info and warnings.warn
+    with mock.patch("sys.version_info", new=mock_version), mock.patch(
         MOCK_WARN
     ) as mock_warn_call:
         _check_python_version()