ci: Update CI to test 3.12 and 3.13

.github/workflows/ci.yaml

@@ -51,7 +51,7 @@ jobs:
       fail-fast: false
       matrix:
         os: [ "ubuntu-latest" ]
-        python-version: [ "3.9", "3.10", "3.11" ]
+        python-version: [ "3.9", "3.10", "3.11", "3.12", "3.13"  ]
     runs-on: "${{ matrix.os }}"
     defaults:
       run:
@@ -87,7 +87,7 @@ jobs:
       fail-fast: false
       matrix:
         os: [ "ubuntu-latest" ]
-        python-version: [ "3.9", "3.10", "3.11" ]
+        python-version: [ "3.9", "3.10", "3.11", "3.12", "3.13" ]
     runs-on: "${{ matrix.os }}"
     steps:
       - name: Check out repository

changelog/58.docs.md

@@ -0,0 +1 @@
+Recorded the strategy for supported Python versions and dependencies

changelog/58.trivial.md

@@ -0,0 +1 @@
+Added support for Python 3.12 and 3.13

docs/development.md

@@ -75,6 +75,27 @@ The steps required are the following:
 
 1. Enjoy the newly available version
 
+## Testing strategy
+
+We support Python 3.9 and above.
+We follow the [Python life-cycle schedule](https://devguide.python.org/versions/) 
+and will drop support for Python versions when they reach their end of life.
+Given the nature of the package,
+we want to ensure support for a broad range of Python versions to minimise any downstream constraints.
+Libraries building on `openscm-units` are free to further restrict the Python versions 
+(or other dependencies) they support.
+
+For downstream package maintainers we recommend following
+the [SPEC 0000](https://scientific-python.org/specs/spec-0000/) deprecation policy.
+This policy provides support for a key scientific packages for 24 months after release
+and Python versions for 36 months after release.
+The Python ecosystem is quicker to adopt new versions than it was previously
+and these reduced support timelines reflect that.
+
+None-the-less we also recommend that lockfiles are used for analysis projects
+to capture the exact versions of dependencies used.
+This will enable the project to be recreated in the future even if the Python version is no longer supported.
+
 ## Read the Docs
 
 Our documentation is hosted by [Read the Docs (RtD)](https://www.readthedocs.org/),

pyproject.toml

@@ -21,11 +21,15 @@ readme = "README.md"
 classifiers = [
     "Development Status :: 5 - Production/Stable",
     "Intended Audience :: Developers",
+    "Intended Audience :: Science/Research",
     "License :: OSI Approved :: BSD License",
     "Operating System :: OS Independent",
     "Programming Language :: Python :: 3.9",
     "Programming Language :: Python :: 3.10",
     "Programming Language :: Python :: 3.11",
+    "Programming Language :: Python :: 3.12",
+    "Programming Language :: Python :: 3.13",
+    "Topic :: Scientific/Engineering",
 ]
 
 [build-system]