Remove Python 3.9 support

CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Removed
+
+- Removed support for Python 3.9. ([#488](https://github.com/heroku/buildpacks-python/pull/488))
+
 ## [3.0.2] - 2026-01-05
 
 ### Changed

src/main.rs

@@ -94,30 +94,6 @@ impl Buildpack for PythonBuildpack {
         }
 
         if let RequestedPythonVersion {
-            major: 3,
-            minor: 9,
-            origin,
-            ..
-        } = &requested_python_version
-        {
-            log_warning(
-                "Support for Python 3.9 is ending soon",
-                formatdoc! {"
-                    Python 3.9 reached its upstream end-of-life on 31st October 2025,
-                    and so no longer receives security updates:
-                    https://devguide.python.org/versions/#supported-versions
-
-                    As such, support for Python 3.9 will be removed from this
-                    buildpack on 7th January 2026.
-
-                    Upgrade to a newer Python version as soon as possible, by
-                    changing the version in your {origin} file.
-
-                    For more information, see:
-                    https://devcenter.heroku.com/articles/python-support#supported-python-versions
-                "},
-            );
-        } else if let RequestedPythonVersion {
             major: 3,
             minor: 10,
             origin,

src/python_version.rs

@@ -16,12 +16,11 @@ pub(crate) const DEFAULT_PYTHON_VERSION: RequestedPythonVersion = RequestedPytho
 #[cfg(test)]
 pub(crate) const DEFAULT_PYTHON_FULL_VERSION: PythonVersion = LATEST_PYTHON_3_14;
 
-pub(crate) const OLDEST_SUPPORTED_PYTHON_3_MINOR_VERSION: u16 = 9;
+pub(crate) const OLDEST_SUPPORTED_PYTHON_3_MINOR_VERSION: u16 = 10;
 pub(crate) const NEWEST_SUPPORTED_PYTHON_3_MINOR_VERSION: u16 = 14;
 pub(crate) const NEXT_UNRELEASED_PYTHON_3_MINOR_VERSION: u16 =
     NEWEST_SUPPORTED_PYTHON_3_MINOR_VERSION + 1;
 
-pub(crate) const LATEST_PYTHON_3_9: PythonVersion = PythonVersion::new(3, 9, 25);
 pub(crate) const LATEST_PYTHON_3_10: PythonVersion = PythonVersion::new(3, 10, 19);
 pub(crate) const LATEST_PYTHON_3_11: PythonVersion = PythonVersion::new(3, 11, 14);
 pub(crate) const LATEST_PYTHON_3_12: PythonVersion = PythonVersion::new(3, 12, 12);
@@ -173,7 +172,6 @@ pub(crate) fn resolve_python_version(
         (3, NEXT_UNRELEASED_PYTHON_3_MINOR_VERSION.., _) | (4.., _, _) => Err(
             ResolvePythonVersionError::UnknownVersion(requested_python_version.clone()),
         ),
-        (3, 9, None) => Ok(LATEST_PYTHON_3_9),
         (3, 10, None) => Ok(LATEST_PYTHON_3_10),
         (3, 11, None) => Ok(LATEST_PYTHON_3_11),
         (3, 12, None) => Ok(LATEST_PYTHON_3_12),
@@ -284,13 +282,13 @@ mod tests {
     fn read_requested_python_version_python_version_file() {
         assert_eq!(
             read_requested_python_version(
-                Path::new("tests/fixtures/python_3.9"),
+                Path::new("tests/fixtures/python_3.13"),
                 PackageManager::Pip
             )
             .unwrap(),
             RequestedPythonVersion {
                 major: 3,
-                minor: 9,
+                minor: 13,
                 patch: None,
                 origin: PythonVersionOrigin::PythonVersionFile,
             }

tests/django_test.rs

@@ -49,8 +49,7 @@ fn django_staticfiles_latest_django() {
     );
 }
 
-// This tests the oldest Django version that works on Python 3.9 (which is the
-// oldest Python that is available on all of our supported builders).
+// This tests the oldest Django version that works on Python 3.10 (our oldest supported Python version).
 #[test]
 #[ignore = "integration test"]
 fn django_staticfiles_legacy_django() {
@@ -63,7 +62,7 @@ fn django_staticfiles_legacy_django() {
                 indoc! {"
                     [Generating Django static files]
                     Running 'manage.py collectstatic'
-                    {'CPATH': '/layers/heroku_python/venv/include:/layers/heroku_python/python/include/python3.9:/layers/heroku_python/python/include:/invalid',
+                    {'CPATH': '/layers/heroku_python/venv/include:/layers/heroku_python/python/include/python3.10:/layers/heroku_python/python/include:/invalid',
                      'DJANGO_SETTINGS_MODULE': 'testproject.settings',
                      'LC_CTYPE': 'C.UTF-8',
                      'LD_LIBRARY_PATH': '/layers/heroku_python/venv/lib:/layers/heroku_python/pip/lib:/layers/heroku_python/python/lib:/invalid',
@@ -81,11 +80,10 @@ fn django_staticfiles_legacy_django() {
 
                     ['/workspace',
                      '/invalid',
-                     '/layers/heroku_python/python/lib/python39.zip',
-                     '/layers/heroku_python/python/lib/python3.9',
-                     '/layers/heroku_python/python/lib/python3.9/lib-dynload',
-                     '/layers/heroku_python/venv/lib/python3.9/site-packages']
-                    Copying '/workspace/testapp/static/robots.txt'
+                     '/layers/heroku_python/python/lib/python310.zip',
+                     '/layers/heroku_python/python/lib/python3.10',
+                     '/layers/heroku_python/python/lib/python3.10/lib-dynload',
+                     '/layers/heroku_python/venv/lib/python3.10/site-packages']
 
                     1 static file copied to '/workspace/staticfiles'.
                 "}

tests/fixtures/django_staticfiles_legacy_django/.python-version

@@ -1 +1 @@
-3.9
+3.10

tests/fixtures/django_staticfiles_legacy_django/requirements.txt

@@ -1,3 +1,2 @@
-# This is the oldest Django version that works on Python 3.9 (which is the
-# oldest Python that is available on all of our supported builders).
-Django==1.8.19
+# This is the oldest Django version that works on Python 3.10 (our oldest supported Python version).
+Django==2.1.15

tests/fixtures/pip_oldest_python/.python-version

@@ -1,3 +1,3 @@
 # This uses the .0 patch version of the oldest major Python version we support,
 # so we can check that the pip bootstrapping works with the oldest bundled pip.
-3.9.0
+3.10.0

tests/fixtures/poetry_oldest_python/.python-version

@@ -1 +1 @@
-3.9.0
+3.10.0

tests/fixtures/poetry_oldest_python/pyproject.toml

@@ -2,5 +2,5 @@
 package-mode = false
 
 [tool.poetry.dependencies]
-python = "^3.9"
+python = "^3.10"
 typing-extensions = "*"

tests/fixtures/python_version_eol/.python-version

@@ -1 +1 @@
-3.8
+3.9

tests/fixtures/runtime_txt_and_python_version_file/runtime.txt

@@ -1 +0,0 @@
-python-3.9.0

tests/fixtures/uv_oldest_python/.python-version

@@ -1 +1 @@
-3.9.0
+3.10.0

tests/fixtures/uv_oldest_python/pyproject.toml

@@ -1,7 +1,7 @@
 [project]
 name = "uv-oldest-python"
 version = "0.0.0"
-requires-python = "==3.9.*"
+requires-python = "==3.10.*"
 dependencies = [
     "typing-extensions",
 ]

tests/pip_test.rs

@@ -237,15 +237,15 @@ fn pip_oldest_python() {
             context.pack_stdout,
             indoc! {"
                 [Determining Python version]
-                Using Python version 3.9.0 specified in .python-version
+                Using Python version 3.10.0 specified in .python-version
 
-                [Warning: Support for Python 3.9 is ending soon]
-                Python 3.9 reached its upstream end-of-life on 31st October 2025,
-                and so no longer receives security updates:
+                [Warning: Support for Python 3.10 is deprecated]
+                Python 3.10 will reach its upstream end-of-life in October 2026,
+                at which point it will no longer receive security updates:
                 https://devguide.python.org/versions/#supported-versions
 
-                As such, support for Python 3.9 will be removed from this
-                buildpack on 7th January 2026.
+                As such, support for Python 3.10 will be removed from this
+                buildpack on 6th January 2027.
 
                 Upgrade to a newer Python version as soon as possible, by
                 changing the version in your .python-version file.
@@ -255,7 +255,7 @@ fn pip_oldest_python() {
 
 
                 [Installing Python]
-                Installing Python 3.9.0
+                Installing Python 3.10.0
             "}
         );
     });

tests/poetry_test.rs

@@ -241,15 +241,15 @@ fn poetry_oldest_python() {
             context.pack_stdout,
             &formatdoc! {"
                 [Determining Python version]
-                Using Python version 3.9.0 specified in .python-version
+                Using Python version 3.10.0 specified in .python-version
 
-                [Warning: Support for Python 3.9 is ending soon]
-                Python 3.9 reached its upstream end-of-life on 31st October 2025,
-                and so no longer receives security updates:
+                [Warning: Support for Python 3.10 is deprecated]
+                Python 3.10 will reach its upstream end-of-life in October 2026,
+                at which point it will no longer receive security updates:
                 https://devguide.python.org/versions/#supported-versions
 
-                As such, support for Python 3.9 will be removed from this
-                buildpack on 7th January 2026.
+                As such, support for Python 3.10 will be removed from this
+                buildpack on 6th January 2027.
 
                 Upgrade to a newer Python version as soon as possible, by
                 changing the version in your .python-version file.
@@ -259,7 +259,7 @@ fn poetry_oldest_python() {
 
 
                 [Installing Python]
-                Installing Python 3.9.0
+                Installing Python 3.10.0
 
                 [Installing Poetry]
                 Installing Poetry {POETRY_VERSION}

tests/python_version_test.rs

@@ -1,6 +1,6 @@
 use crate::python_version::{
-    DEFAULT_PYTHON_FULL_VERSION, DEFAULT_PYTHON_VERSION, LATEST_PYTHON_3_9, LATEST_PYTHON_3_10,
-    LATEST_PYTHON_3_11, LATEST_PYTHON_3_12, LATEST_PYTHON_3_13, LATEST_PYTHON_3_14,
+    DEFAULT_PYTHON_FULL_VERSION, DEFAULT_PYTHON_VERSION, LATEST_PYTHON_3_10, LATEST_PYTHON_3_11,
+    LATEST_PYTHON_3_12, LATEST_PYTHON_3_13, LATEST_PYTHON_3_14,
     NEWEST_SUPPORTED_PYTHON_3_MINOR_VERSION, PythonVersion,
 };
 use crate::tests::default_build_config;
@@ -29,12 +29,6 @@ fn python_version_unspecified() {
     });
 }
 
-#[test]
-#[ignore = "integration test"]
-fn python_3_9() {
-    builds_with_python_version("tests/fixtures/python_3.9", &LATEST_PYTHON_3_9);
-}
-
 #[test]
 #[ignore = "integration test"]
 fn python_3_10() {
@@ -75,33 +69,7 @@ fn builds_with_python_version(fixture_path: &str, python_version: &PythonVersion
     TestRunner::default().build(default_build_config(fixture_path), |context| {
         assert_empty!(context.pack_stderr);
 
-        if major == 3 && minor == 9 {
-            assert_contains!(
-                context.pack_stdout,
-                &formatdoc! {"
-                    [Determining Python version]
-                    Using Python version {major}.{minor} specified in .python-version
-
-                    [Warning: Support for Python 3.9 is ending soon]
-                    Python 3.9 reached its upstream end-of-life on 31st October 2025,
-                    and so no longer receives security updates:
-                    https://devguide.python.org/versions/#supported-versions
-
-                    As such, support for Python 3.9 will be removed from this
-                    buildpack on 7th January 2026.
-
-                    Upgrade to a newer Python version as soon as possible, by
-                    changing the version in your .python-version file.
-
-                    For more information, see:
-                    https://devcenter.heroku.com/articles/python-support#supported-python-versions
-
-
-                    [Installing Python]
-                    Installing Python {major}.{minor}.{patch}
-                "}
-            );
-        } else if major == 3 && minor == 10 {
+        if major == 3 && minor == 10 {
             assert_contains!(
                 context.pack_stdout,
                 &formatdoc! {"
@@ -154,9 +122,8 @@ fn builds_with_python_version(fixture_path: &str, python_version: &PythonVersion
 
                 # Check that the Python binary is using its own 'libpython' and not the system one:
                 # https://github.com/docker-library/python/issues/784
-                # Note: This has to handle Python 3.9 and older not being built in shared library mode.
-                libpython_path=$(ldd /layers/heroku_python/python/bin/python | grep libpython || true)
-                if [[ -n "${libpython_path}" && "${libpython_path}" != *"=> /layers/"* ]]; then
+                libpython_path=$(ldd /layers/heroku_python/python/bin/python | grep libpython)
+                if [[ "${libpython_path}" != *"=> /layers/"* ]]; then
                   echo "The Python binary is not using the correct libpython!"
                   echo "${libpython_path}"
                   exit 1
@@ -326,14 +293,14 @@ fn python_version_eol() {
                 [Determining Python version]
 
                 [Error: The requested Python version has reached end-of-life]
-                Python 3.8 has reached its upstream end-of-life, and is
+                Python 3.9 has reached its upstream end-of-life, and is
                 therefore no longer receiving security updates:
                 https://devguide.python.org/versions/#supported-versions
 
                 As such, it's no longer supported by this buildpack:
                 https://devcenter.heroku.com/articles/python-support#supported-python-versions
 
-                Please upgrade to at least Python 3.9 by changing the
+                Please upgrade to at least Python 3.10 by changing the
                 version in your .python-version file.
 
                 If possible, we recommend upgrading all the way to Python {DEFAULT_PYTHON_VERSION},

tests/uv_test.rs

@@ -242,15 +242,15 @@ fn uv_oldest_python() {
             context.pack_stdout,
             &formatdoc! {"
                 \\[Determining Python version\\]
-                Using Python version 3.9.0 specified in .python-version
+                Using Python version 3.10.0 specified in .python-version
 
-                \\[Warning: Support for Python 3.9 is ending soon\\]
-                Python 3.9 reached its upstream end-of-life on 31st October 2025,
-                and so no longer receives security updates:
+                \\[Warning: Support for Python 3.10 is deprecated\\]
+                Python 3.10 will reach its upstream end-of-life in October 2026,
+                at which point it will no longer receive security updates:
                 https://devguide.python.org/versions/#supported-versions
 
-                As such, support for Python 3.9 will be removed from this
-                buildpack on 7th January 2026.
+                As such, support for Python 3.10 will be removed from this
+                buildpack on 6th January 2027.
 
                 Upgrade to a newer Python version as soon as possible, by
                 changing the version in your .python-version file.
@@ -260,7 +260,7 @@ fn uv_oldest_python() {
 
 
                 \\[Installing Python\\]
-                Installing Python 3.9.0
+                Installing Python 3.10.0
 
                 \\[Installing uv\\]
                 Installing uv {UV_VERSION}