feat(core): warn when importing on Python 3.10.

Emit a FutureWarning at import time when running on Python < 3.11 using
a fixed per-release version tuple rather than a runtime calendar check.

Author: lahirumaramba

README.md

@@ -43,10 +43,11 @@ requests, code review feedback, and also pull requests.
 
 ## Supported Python Versions
 
-We currently support Python 3.10+. However, Python 3.10 support is deprecated,
-and developers are strongly advised to use Python 3.11 or higher. Firebase
-Admin Python SDK is also tested on PyPy and
-[Google App Engine](https://cloud.google.com/appengine/) environments.
+We currently support Python 3.10+. However, Python 3.10 support is deprecated
+and will be dropped in an upcoming minor release. Developers are strongly
+advised to use Python 3.11 or higher. Firebase Admin Python SDK is also tested
+on PyPy and [Google App Engine](https://cloud.google.com/appengine/)
+environments.
 
 
 ## Documentation

firebase_admin/__init__.py

@@ -21,9 +21,14 @@
 from google.auth.credentials import Credentials as GoogleAuthCredentials
 from google.auth.exceptions import DefaultCredentialsError
 from firebase_admin import credentials
+from firebase_admin import _python_version_support
 from firebase_admin.__about__ import __version__
 
 
+# Perform Python version check and emit a support warning if needed.
+_python_version_support.check_python_version()
+
+
 _apps = {}
 _apps_lock = threading.RLock()
 _clock = datetime.datetime.utcnow

firebase_admin/_python_version_support.py

@@ -0,0 +1,40 @@
+# Copyright 2026 Google Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Runtime Python version deprecation check for the Firebase Admin SDK."""
+
+import sys
+import warnings
+
+# Minimum Python (major, minor) version that does not emit a deprecation warning.
+# Bump this tuple in a minor release to deprecate an older Python version ahead
+# of dropping it in a future release.
+_MIN_NON_DEPRECATED_VERSION = (3, 11)
+
+
+def check_python_version() -> None:
+    """Emits a FutureWarning if the running Python version is deprecated."""
+    current = (sys.version_info.major, sys.version_info.minor)
+    if current < _MIN_NON_DEPRECATED_VERSION:
+        current_str = f'{current[0]}.{current[1]}'
+        recommended_str = (
+            f'{_MIN_NON_DEPRECATED_VERSION[0]}.{_MIN_NON_DEPRECATED_VERSION[1]}'
+        )
+        warnings.warn(
+            f'Support for Python {current_str} in firebase-admin is deprecated '
+            'and will be dropped in a future minor release. Please upgrade to '
+            f'Python {recommended_str} or higher to continue receiving updates.',
+            FutureWarning,
+            stacklevel=2,
+        )

tests/test_python_version_support.py

@@ -0,0 +1,56 @@
+# Copyright 2026 Google Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Tests for firebase_admin._python_version_support."""
+
+from collections import namedtuple
+from unittest.mock import patch
+import warnings
+
+import pytest
+
+from firebase_admin._python_version_support import check_python_version
+
+_VersionInfo = namedtuple('_VersionInfo', ['major', 'minor'])
+
+
+@pytest.mark.parametrize('version_tuple', [(3, 9), (3, 10)])
+def test_deprecated_python_versions_emit_future_warning(version_tuple):
+    mock_version = _VersionInfo(major=version_tuple[0], minor=version_tuple[1])
+    version_str = f'{version_tuple[0]}.{version_tuple[1]}'
+
+    with patch('firebase_admin._python_version_support.sys.version_info', mock_version):
+        with pytest.warns(FutureWarning) as record:
+            check_python_version()
+
+    assert len(record) == 1
+    assert record[0].filename == __file__
+    expected = (
+        f'Support for Python {version_str} in firebase-admin is deprecated '
+        'and will be dropped in a future minor release. Please upgrade to '
+        'Python 3.11 or higher to continue receiving updates.'
+    )
+    assert str(record[0].message) == expected
+
+
+@pytest.mark.parametrize('version_tuple', [(3, 11), (3, 12), (3, 13), (3, 14), (3, 15)])
+def test_supported_python_versions_do_not_warn(version_tuple):
+    mock_version = _VersionInfo(major=version_tuple[0], minor=version_tuple[1])
+
+    with patch('firebase_admin._python_version_support.sys.version_info', mock_version):
+        with warnings.catch_warnings(record=True) as recorded:
+            warnings.simplefilter('always')
+            check_python_version()
+
+    assert not recorded