Drop python 310 support

.github/workflows/main.yml

@@ -39,7 +39,7 @@ jobs:
     strategy:
       matrix:
         python-version: [
-          "3.10", "3.11", "3.12", "3.13", "3.14", "3.14t", "3.15", "3.15t"
+          "3.11", "3.12", "3.13", "3.14", "3.14t", "3.15", "3.15t"
         ]
         os: [ubuntu-latest, macos-latest, windows-latest]
 

.github/workflows/release.yml

@@ -22,7 +22,7 @@ jobs:
         platform:
           - runner: ubuntu-latest
             target: x86_64
-            interpreters: &full-interpreters '["3.10", "3.11", "3.12", "3.13", "3.14", "3.14t", "3.15", "3.15t"]'
+            interpreters: &full-interpreters '["3.11", "3.12", "3.13", "3.14", "3.14t", "3.15", "3.15t"]'
           - runner: ubuntu-latest
             target: x86
             interpreters: *full-interpreters
@@ -39,7 +39,7 @@ jobs:
           # 3.14/3.14t.
           - runner: ubuntu-latest
             target: armv7
-            interpreters: &cross-interpreters '["3.10", "3.11", "3.12", "3.13", "3.14", "3.14t"]'
+            interpreters: &cross-interpreters '["3.11", "3.12", "3.13", "3.14", "3.14t"]'
           - runner: ubuntu-latest
             target: s390x
             interpreters: *cross-interpreters
@@ -112,7 +112,7 @@ jobs:
         platform:
           - runner: windows-latest
             target: x64
-            interpreters: &interpreters '["3.10", "3.11", "3.12", "3.13", "3.14", "3.15"]'
+            interpreters: &interpreters '["3.11", "3.12", "3.13", "3.14", "3.15"]'
             free-threaded-interpreters: &free-threaded-interpreters '["3.14t", "3.15t"]'
           - runner: windows-latest
             target: x86
@@ -171,7 +171,6 @@ jobs:
       - uses: actions/setup-python@v6
         with:
           python-version: |
-            3.10
             3.11
             3.12
             3.13
@@ -182,7 +181,7 @@ jobs:
         uses: PyO3/maturin-action@v1
         with:
           target: ${{ matrix.platform.target }}
-          args: --release --out dist --interpreter 3.10 3.11 3.12 3.13 3.14 3.15
+          args: --release --out dist --interpreter 3.11 3.12 3.13 3.14 3.15
           sccache: 'true'
 
       # setup-python installs the free-threaded interpreter's binary under the

CHANGELOG.rst

@@ -6,6 +6,7 @@ latest
 ------
 
 * Support multiple packages in ``ImportGraph.nominate_cycle_breakers``.
+* Drop support for Python 3.10.
 
 3.18 (2026-10-26)
 -----------------

CONTRIBUTING.rst

@@ -124,6 +124,78 @@ It's a good idea to run ``just full-check`` before getting a review.
 This will run linters, docs build and tests under every supported Python version.
 You can automatically fix many lint errors using ``just autofix`` (or ``just autofix-python`` and ``just autofix-rust`` separately).
 
+Adding support for a new Python version
+========================================
+
+1. In ``pyproject.toml``, add ``3.x`` to the ``Programming Language :: Python :: 3.x``
+   classifiers.
+2. In ``.github/workflows/main.yml``, add ``"3.x"`` and ``"3.xt"`` to the
+   ``test`` job's ``python-version`` matrix.
+3. In ``.github/workflows/release.yml``, add ``"3.x"`` and ``"3.xt"`` to the shared
+   ``linux`` and ``musllinux`` interpreter lists. For ``windows``, add ``"3.x"`` to
+   the regular interpreter lists (including the ARM64 literal list) and ``"3.xt"``
+   to the free-threaded interpreter lists. For ``macos``, add ``3.x`` to the regular
+   ``actions/setup-python`` list and matching ``--interpreter`` arguments, and ``3.xt``
+   to the corresponding free-threaded step's list and arguments. Keep the regular and
+   free-threaded installations separate on Windows/macOS to avoid binary shadowing.
+4. Push a branch with this change and trigger the release workflow manually, without pushing
+   a tag, to see which targets can actually build the new version::
+
+       gh workflow run release.yml --ref <your-branch>
+
+   Then watch it with ``gh run watch`` or in the Actions tab.
+5. For any ``linux``/``musllinux`` job that fails because the build image doesn't have the
+   new interpreter yet, split that target out of the shared interpreter list it was using
+   (e.g. ``&full-interpreters``/``&cross-interpreters``) into its own list without the new
+   version, following the pattern already used for targets that lag behind (see the comments
+   above the ``linux`` and ``musllinux`` matrices for the current state). To check directly
+   instead of waiting for a failed build, look up the image's available tags:
+
+   - ``linux`` job, native targets (x86_64, x86, aarch64): `quay.io/pypa manylinux2014 tags
+     <https://quay.io/repository/pypa/manylinux2014_x86_64?tab=tags>`_
+   - ``linux`` job, cross targets (armv7, s390x, ppc64le): `rust-cross manylinux2014-cross
+     tags <https://github.com/rust-cross/manylinux-cross/pkgs/container/manylinux2014-cross>`_
+   - ``musllinux`` job (all targets): `rust-cross rust-musl-cross tags
+     <https://github.com/rust-cross/rust-musl-cross/pkgs/container/rust-musl-cross>`_
+   - ``windows``/``macos`` jobs use ``actions/setup-python``, which installs from
+     `actions/python-versions <https://github.com/actions/python-versions/blob/main/versions-manifest.json>`_
+     - these are normally available from Python's own release day, including prereleases
+     (``allow-prereleases: true`` is already set).
+6. For each target excluded in step 5, `open a GitHub issue
+   <https://github.com/python-grimp/grimp/issues/new>`_ to track adding it once the build
+   image catches up (e.g. "Add Python 3.x wheels for musllinux", one issue per image/family
+   is fine if several targets share it). Add a comment directly above the relevant
+   interpreter list in ``release.yml`` referencing the issue number, e.g.::
+
+       # ghcr.io/rust-cross/rust-musl-cross doesn't yet bundle Python 3.x.
+       # See https://github.com/python-grimp/grimp/issues/<n>.
+
+   This is the only thing that makes the gap actionable later - without an issue number
+   there's nothing to revisit the exclusion when the image is updated.
+7. In ``justfile``, add a ``just test-python 3.x`` and ``3.xt`` lines to the ``test-all``
+   recipe.
+8. In ``CHANGELOG.rst``, add an entry under ``latest``: ``* Officially support Python 3.x.``
+   If step 5 excluded any targets, add a second entry noting which ones, why, and linking the
+   issue(s) from step 6 (see existing ``CHANGELOG.rst`` entries about missing 3.15 wheels for
+   the expected wording).
+9. Run ``just full-check`` to confirm everything passes.
+
+Dropping support for a Python version
+======================================
+
+1. In ``pyproject.toml``, update ``requires-python`` and remove the ``Programming Language ::
+   Python :: 3.x`` classifier.
+2. In ``.github/workflows/main.yml``, remove ``"3.x"`` (and ``"3.xt"`` if present) from the
+   ``test`` job's ``python-version`` matrix.
+3. In ``.github/workflows/release.yml``, remove ``"3.x"`` (and ``"3.xt"``) from every
+   interpreter list it appears in.
+4. In ``justfile``, remove the ``just test-python 3.x`` (and ``3.xt``) line(s) from the
+   ``test-all`` recipe.
+5. In ``CHANGELOG.rst``, add an entry under ``latest``: ``* Drop support for Python 3.x.``
+6. Run ``just modernize-python 3x`` with the new lowest version (e.g. ``just modernize-python 311``).
+7. Remove any code paths or tests that exist solely to support the dropped version.
+8. Run ``just full-check`` to confirm everything passes.
+
 Benchmarking
 ============
 

justfile

@@ -33,7 +33,6 @@ test-python $UV_PYTHON=env("UV_PYTHON", ""):
 # Runs tests under all supported Python versions, plus Rust.
 [group('testing')]
 test-all:
-    just test-python 3.10
     just test-python 3.11
     just test-python 3.12
     just test-python 3.13
@@ -118,6 +117,13 @@ lint:
     @echo ''
     @echo '👍 {{GREEN}} Linting all good.{{NORMAL}}'
 
+# Modernize Python code. (E.g. just modernize-python 311)
+[group('linting')]
+modernize-python MIN_VERSION:
+    @find docs src tests -name "*.py" -not -path "tests/assets/*" -exec uv run pyupgrade --py{{MIN_VERSION}}-plus --exit-zero-even-if-changed {} +
+    @just autofix-python
+    @just format-python
+
 # Build docs.
 [group('docs')]
 build-docs:

pyproject.toml

@@ -14,7 +14,7 @@ description = "Builds a queryable graph of the imports within one or more Python
 authors = [
     {name = "David Seddon", email = "david@seddonym.me"},
 ]
-requires-python = ">=3.10"
+requires-python = ">=3.11"
 dependencies = []
 classifiers = [
     "Development Status :: 5 - Production/Stable",
@@ -24,7 +24,6 @@ classifiers = [
     "Operating System :: POSIX",
     "Operating System :: Microsoft :: Windows",
     "Programming Language :: Python",
-    "Programming Language :: Python :: 3.10",
     "Programming Language :: Python :: 3.11",
     "Programming Language :: Python :: 3.12",
     "Programming Language :: Python :: 3.13",
@@ -60,6 +59,7 @@ dev = [
     "requests==2.32.3",
     "sqlalchemy==2.0.35",
     "google-cloud-audit-log==0.3.0",
+    "pyupgrade>=3.21.2",
 ]
 docs = [
     "sphinx>=7.4.7",

src/grimp/application/ports/timing.py

@@ -2,6 +2,7 @@
 
 import abc
 from types import TracebackType
+from typing import Self
 
 
 class Timer(abc.ABC):
@@ -22,7 +23,7 @@ def __init__(self) -> None:
         # We use a stack so context managers can be nested.
         self._start_stack: list[float] = []
 
-    def __enter__(self) -> Timer:
+    def __enter__(self) -> Self:
         self._start_stack.append(self.get_current_time())
         return self
 

tests/adaptors/filesystem.py

@@ -91,7 +91,7 @@ def walk(self, directory_name):
 
     def _walk_contents(
         self, directory_contents: dict[str, Any], containing_directory: str
-    ) -> Generator[tuple[str, list[str], list[str]], None, None]:
+    ) -> Generator[tuple[str, list[str], list[str]]]:
         directories = []
         files = []
         for key, value in directory_contents.items():

tests/unit/application/graph/test_manipulation.py

@@ -1,8 +1,7 @@
 import re
-from typing import TypedDict
+from typing import NotRequired, TypedDict
 
 import pytest
-from typing_extensions import NotRequired  # Can move to typing once drop support for 3.10.
 
 from grimp.application.graph import ImportGraph
 from grimp.exceptions import ModuleNotPresent