feat: drop Python 3.9 (#1049)

henryiii · web-flow · commit 64ddef9b7090 · 2026-04-16T17:31:06.000-04:00
* feat: drop Python 3.9

Signed-off-by: Henry Schreiner &lt;henryfs@princeton.edu&gt;

* tests: fix 3.9/3.10 -&gt; 3.10/3.11

Assisted-by: OpenCode:Kimi-K2.5
Signed-off-by: Henry Schreiner &lt;henryschreineriii@gmail.com&gt;

* chore: clean up a few more mentions of old Python versions

Signed-off-by: Henry Schreiner &lt;henryschreineriii@gmail.com&gt;
Assisted-by: OpenCode:Kimi-K2.5

* chore: use more pattern matching

Assisted-by: OpenCode:Kimi-K2.5
Signed-off-by: Henry Schreiner &lt;henryschreineriii@gmail.com&gt;

* tests: fix coverage issue

Signed-off-by: Henry Schreiner &lt;henryfs@princeton.edu&gt;

---------

Signed-off-by: Henry Schreiner &lt;henryfs@princeton.edu&gt;
Signed-off-by: Henry Schreiner &lt;henryschreineriii@gmail.com&gt;
diff --git a/.github/ISSUE_TEMPLATE/bug.yml b/.github/ISSUE_TEMPLATE/bug.yml
@@ -31,9 +31,9 @@ body:
       label: Environment
       description: |
         examples:
-          - **OS**: Ubuntu 20.04
-          - **Python**: 3.9.7
-          - **Nox**: 0.14.2
+          - **OS**: Ubuntu 24.04
+          - **Python**: 3.14.3
+          - **Nox**: 2026.04.10
       value: |
         - OS:
         - Python:
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
@@ -23,14 +23,14 @@ jobs:
       matrix:
         os: [ubuntu-latest, windows-latest, macos-latest]
         python-version:
-          - "3.9"
-          - "3.11"
+          - "3.10"
+          - "3.12"
           - "3.14"
         include:
-          - os: ubuntu-22.04
-            python-version: "3.9"
           - os: ubuntu-22.04
             python-version: "3.11"
+          - os: ubuntu-22.04
+            python-version: "3.13"
           - os: macos-15-intel
             python-version: "3.12"
     steps:
@@ -41,8 +41,8 @@ jobs:
         uses: actions/setup-python@v6
         with:
           python-version: |
-            3.9
             3.10
+            3.11
       - name: Set up Python ${{ matrix.python-version }}
         uses: actions/setup-python@v6
         with:
diff --git a/action.yml b/action.yml
@@ -15,7 +15,7 @@ runs:
     - uses: actions/setup-python@a309ff8b426b58ec0e2a45f0f869d46889d02405 # v6.2.0
       id: localpython
       with:
-        python-version: "3.9 - 3.14"
+        python-version: "3.10 - 3.14"
         update-environment: false
 
     - name: "Validate input"
diff --git a/docs/config.rst b/docs/config.rst
@@ -114,8 +114,8 @@ You can tell Nox to use a different Python interpreter/version by specifying the
 .. note::
 
     The Python binaries on Windows are found via the Python `Launcher`_ for
-    Windows (``py``). For example, Python 3.9 can be found by determining which
-    executable is invoked by ``py -3.9``. If a given test needs to use the 32-bit
+    Windows (``py``). For example, Python 3.10 can be found by determining which
+    executable is invoked by ``py -3.10``. If a given test needs to use the 32-bit
     version of a given Python, then ``X.Y-32`` should be used as the version.
 
     .. _Launcher: https://docs.python.org/3/using/windows.html#python-launcher-for-windows
@@ -142,19 +142,19 @@ When collecting your sessions, Nox will create a separate session for each inter
 
 .. code-block:: python
 
-    @nox.session(python=['2.7', '3.6', '3.7', '3.8', '3.9'])
+    @nox.session(python=['3.10', '3.11', '3.12', '3.13', '3.14'])
     def tests(session):
         pass
 
 Will produce these sessions:
 
 .. code-block:: console
 
-    * tests-2.7
-    * tests-3.6
-    * tests-3.7
-    * tests-3.8
-    * tests-3.9
+    * tests-3.10
+    * tests-3.11
+    * tests-3.12
+    * tests-3.13
+    * tests-3.14
 
 Note that this expansion happens *before* parameterization occurs, so you can still parametrize sessions with multiple interpreters.
 
diff --git a/docs/usage.rst b/docs/usage.rst
@@ -245,11 +245,11 @@ In addition to Nox supporting executing single sessions, it also supports runnin
 
    .. code-tab:: console CLI options
 
-         nox --extra-pythons 3.8 3.9 3.10
+         nox --extra-pythons 3.12 3.13 3.14
 
    .. code-tab:: console Environment variables
 
-         NOXEXTRAPYTHON=3.8,3.9,3.10 nox
+         NOXEXTRAPYTHON=3.12,3.13,3.14 nox
 
 
 This will, in addition to specified Python versions in the Noxfile, also create sessions for the specified versions.
diff --git a/nox/_decorators.py b/nox/_decorators.py
@@ -18,7 +18,8 @@
 import functools
 import inspect
 import types
-from typing import TYPE_CHECKING, Any, Callable, Literal, TypeVar, cast
+from collections.abc import Callable
+from typing import TYPE_CHECKING, Any, Literal, TypeVar, cast
 
 if TYPE_CHECKING:
     from collections.abc import Iterable, Mapping, Sequence
diff --git a/nox/_option_set.py b/nox/_option_set.py
@@ -47,7 +47,7 @@ def __dir__() -> list[str]:
 
 
 av_opt_str = av.optional(av.instance_of(str))
-av_opt_path = av.optional(av.or_(av.instance_of(str), av.instance_of(os.PathLike)))
+av_opt_path = av.optional(av.or_(av.instance_of(str), av.instance_of(os.PathLike)))  # type: ignore[type-abstract]
 av_opt_list_str = av.optional(
     av.deep_iterable(
         member_validator=av.instance_of(str),
diff --git a/nox/_options.py b/nox/_options.py
@@ -21,7 +21,7 @@
 import itertools
 import os
 import sys
-from typing import TYPE_CHECKING, Any, Callable, Literal
+from typing import TYPE_CHECKING, Any, Literal
 
 import argcomplete
 
@@ -30,7 +30,7 @@
 from nox.virtualenv import ALL_VENVS
 
 if TYPE_CHECKING:
-    from collections.abc import Iterable, Sequence
+    from collections.abc import Callable, Iterable, Sequence
 
     from nox._option_set import NoxOptions
 
diff --git a/nox/_parametrize.py b/nox/_parametrize.py
@@ -17,7 +17,7 @@
 import functools
 import itertools
 from collections.abc import Iterable
-from typing import TYPE_CHECKING, Any, Union
+from typing import TYPE_CHECKING, Any
 
 if TYPE_CHECKING:
     from collections.abc import Callable, Sequence
@@ -64,7 +64,7 @@ def __init__(
 
     @property
     def call_spec(self) -> dict[str, Any]:
-        return dict(zip(self.arg_names, self.args))
+        return dict(zip(self.arg_names, self.args, strict=True))
 
     def __str__(self) -> str:
         if self.id:
@@ -96,7 +96,7 @@ def __eq__(self, other: object) -> bool:
                 and self.tags == other.tags
             )
         if isinstance(other, dict):
-            return dict(zip(self.arg_names, self.args)) == other
+            return dict(zip(self.arg_names, self.args, strict=True)) == other
 
         return NotImplemented
 
@@ -108,7 +108,7 @@ def _apply_param_specs(param_specs: Iterable[Param], f: Any) -> Any:
     return f
 
 
-ArgValue = Union[Param, Iterable[Any]]
+ArgValue = Param | Iterable[Any]
 
 
 def parametrize_decorator(
diff --git a/nox/_typing.py b/nox/_typing.py
@@ -15,7 +15,6 @@
 from __future__ import annotations
 
 from collections.abc import Sequence
-from typing import Union
 
 __all__ = ["Python"]
 
@@ -24,4 +23,4 @@ def __dir__() -> list[str]:
     return __all__
 
 
-Python = Union[str, Sequence[str], bool, None]
+Python = str | Sequence[str] | bool | None
diff --git a/nox/_version.py b/nox/_version.py
@@ -41,27 +41,23 @@ def get_nox_version() -> str:
     return metadata.version("nox")
 
 
-def _parse_string_constant(node: ast.AST) -> str | None:  # pragma: no cover
-    """Return the value of a string constant."""
-    if isinstance(node, ast.Constant) and isinstance(node.value, str):
-        return node.value
-    return None
-
-
 def _parse_needs_version(source: str, filename: str = "<unknown>") -> str | None:
     """Parse ``nox.needs_version`` from the user's Noxfile."""
     value: str | None = None
     module: ast.Module = ast.parse(source, filename=filename)
     for statement in module.body:
-        if isinstance(statement, ast.Assign):
-            for target in statement.targets:
-                if (
-                    isinstance(target, ast.Attribute)
-                    and isinstance(target.value, ast.Name)
-                    and target.value.id == "nox"
-                    and target.attr == "needs_version"
-                ):
-                    value = _parse_string_constant(statement.value)
+        match statement:
+            case ast.Assign(
+                targets=[
+                    ast.Attribute(
+                        value=ast.Name(id="nox"),
+                        attr="needs_version",
+                    ),
+                    *_,
+                ],
+                value=ast.Constant(value=str() as constant_value),
+            ):
+                value = constant_value
     return value
 
 
diff --git a/nox/project.py b/nox/project.py
@@ -57,12 +57,14 @@ def myscript(session):
             session.install(*myscript_options["dependencies"])
     """
     filepath = Path(filename)
-    if filepath.suffix == ".toml":
-        return _load_toml_file(filepath)
-    if filepath.suffix in {".py", ""}:
-        return _load_script_block(filepath, missing_ok=missing_ok)
-    msg = f"Extension must be .py or .toml, got {filepath.suffix}"
-    raise ValueError(msg)
+    match filepath.suffix:
+        case ".toml":
+            return _load_toml_file(filepath)
+        case ".py" | "":
+            return _load_script_block(filepath, missing_ok=missing_ok)
+        case suffix:
+            msg = f"Extension must be .py or .toml, got {suffix}"
+            raise ValueError(msg)
 
 
 def _load_toml_file(filepath: Path) -> dict[str, Any]:
diff --git a/nox/registry.py b/nox/registry.py
@@ -17,7 +17,8 @@
 import copy
 import functools
 import warnings
-from typing import TYPE_CHECKING, Any, Callable, Literal, overload
+from collections.abc import Callable
+from typing import TYPE_CHECKING, Any, Literal, overload
 
 from ._decorators import Func
 
diff --git a/nox/sessions.py b/nox/sessions.py
@@ -1278,28 +1278,29 @@ def imperfect(self) -> str:
         Returns:
             str: A word or phrase representing the status.
         """
-        if self.status == Status.SUCCESS:
-            return "was successful" + _duration_str(self.duration, " in {time}")
-
-        status = self.status.name.lower()
-        if self.reason:
-            duration_err = _duration_str(self.duration, " (took {time})")
-            return f"{status}: {self.reason}{duration_err}"
-        return status
+        match self.status:
+            case Status.SUCCESS:
+                return "was successful" + _duration_str(self.duration, " in {time}")
+            case _:
+                status = self.status.name.lower()
+                if self.reason:
+                    duration_err = _duration_str(self.duration, " (took {time})")
+                    return f"{status}: {self.reason}{duration_err}"
+                return status
 
     def log(self, message: str) -> None:
         """Log a message using the appropriate log function.
 
         Args:
             message (str): The message to be logged.
         """
-        log_function = logger.info
-        if self.status == Status.SUCCESS:
-            log_function = logger.success
-        if self.status == Status.SKIPPED:
-            log_function = logger.warning
-        if self.status.value <= 0:
-            log_function = logger.error
+        match self.status:
+            case Status.SUCCESS:
+                log_function = logger.success
+            case Status.SKIPPED:
+                log_function = logger.warning
+            case status:
+                log_function = logger.error if status.value <= 0 else logger.info
         log_function(message)
 
     def serialize(self) -> dict[str, Any]:
diff --git a/nox/virtualenv.py b/nox/virtualenv.py
diff --git a/noxfile.py b/noxfile.py
diff --git a/pyproject.toml b/pyproject.toml
diff --git a/tests/conftest.py b/tests/conftest.py
diff --git a/tests/resources/noxfile_requires.py b/tests/resources/noxfile_requires.py
diff --git a/tests/test_main.py b/tests/test_main.py
diff --git a/tests/test_project.py b/tests/test_project.py
