Add Python 3.9 deprecation notice (#4654)

Author: nateprewitt

README.rst

@@ -17,6 +17,11 @@ Boto (pronounced boh-toh) was named after the fresh water dolphin native to the
 Notices
 -------
 
+On 2026-04-29, support for Python 3.9 will end for Boto3. This follows the
+Python Software Foundation `end of support <https://peps.python.org/pep-0596/#lifespan>`__
+for the runtime which occurred on 2025-10-31.
+For more information, see this `blog post <https://aws.amazon.com/blogs/developer/python-support-policy-updates-for-aws-sdks-and-tools/>`__.
+
 On 2025-04-22, support for Python 3.8 ended for Boto3. This follows the
 Python Software Foundation `end of support <https://peps.python.org/pep-0569/#lifespan>`__
 for the runtime which occurred on 2024-10-07.

boto3/compat.py

@@ -60,16 +60,16 @@ def filter_python_deprecation_warnings():
 
 def _warn_deprecated_python():
     """Use this template for future deprecation campaigns as needed."""
-    py_37_params = {
-        'date': 'December 13, 2023',
+    py_39_params = {
+        'date': 'April 29, 2026',
         'blog_link': (
             'https://aws.amazon.com/blogs/developer/'
             'python-support-policy-updates-for-aws-sdks-and-tools/'
         )
     }
     deprecated_versions = {
         # Example template for future deprecations
-        (3, 7): py_37_params,
+        (3, 9): py_39_params,
     }
     py_version = sys.version_info[:2]
 
@@ -78,7 +78,7 @@ def _warn_deprecated_python():
         warning = (
             "Boto3 will no longer support Python {}.{} "
             "starting {}. To continue receiving service updates, "
-            "bug fixes, and security updates please upgrade to Python 3.8 or "
+            "bug fixes, and security updates please upgrade to Python 3.10 or "
             "later. More information can be found here: {}"
         ).format(py_version[0], py_version[1], params['date'], params['blog_link'])
         warnings.warn(warning, PythonDeprecationWarning)

docs/source/guide/quickstart.rst

@@ -24,11 +24,9 @@ To use Boto3, you first need to install it and its dependencies.
 Install or update Python
 ~~~~~~~~~~~~~~~~~~~~~~~~
 
-Before installing Boto3, install Python 3.9 or later; support for Python 3.8 and
-earlier is deprecated. After the deprecation date listed for each Python
-version, new releases of Boto3 will not include support for that version of
-Python. For details, including the deprecation schedule and how to update your
-project to use Python 3.9, see :ref:`guide_migration_py3`.
+Before installing Boto3, ensure you're using Python 3.10 or later.
+For details on how to update your project from older versions of Python,
+see :ref:`guide_migration_py3`.
 
 For information about how to get the latest version of Python, see the official `Python
 documentation <https://www.python.org/downloads/>`_.