Revert "Drop support for Python 3.9"

This reverts commit a054afb.

Author: dstansby

.github/ISSUE_TEMPLATE/bug_report.yml

@@ -27,7 +27,7 @@ body:
     attributes:
       label: Python Version
       description: Version of Python interpreter
-      placeholder: 3.10, 3.11, 3.12 etc.
+      placeholder: 3.9, 3.10, 3.11, etc.
     validations:
       required: true
   - type: input

.github/workflows/python-package.yml

@@ -15,7 +15,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: ['3.10', '3.11', '3.12']
+        python-version: ['3.9', '3.10', '3.11', '3.12']
         numpy_version: ['>=1.24.0', '==1.23.*']
         exclude:
           - python-version: '3.10'

.github/workflows/releases.yml

@@ -19,7 +19,7 @@ jobs:
       - uses: actions/setup-python@v5.1.0
         name: Install Python
         with:
-          python-version: '3.11'
+          python-version: '3.9'
 
       - name: Install PyBuild
         run: |

.readthedocs.yaml

@@ -3,7 +3,7 @@ version: 2
 build:
   os: ubuntu-20.04
   tools:
-    python: "3.11"
+    python: "3.9"
 
 sphinx:
   configuration: docs/conf.py

docs/release.rst

@@ -24,13 +24,7 @@ Enhancements
 ~~~~~~~~~~~~
 
 * Add Zstd codec to old V3 code path.
-  By :user:`Ryan Abernathey <rabernat>`
-
-Maintenance
-~~~~~~~~~~~
-
-* Removed support for Python 3.9.
-  By :user:`David Stansby <dstansby>`
+  By :user:`Ryan Abernathey <rabernat>` 
 
 .. _release_2.18.1:
 
@@ -57,7 +51,7 @@ Maintenance
 * Enable ruff/bugbear rules (B) and fix issues.
   By :user:`Dimitri Papadopoulos Orfanos <DimitriPapadopoulos>` :issue:`1702`.
 
-* Minor updates to use `np.inf` instead of `np.PINF` / `np.NINF` in preparation for NumPy 2.0.0 release.
+* Minor updates to use `np.inf` instead of `np.PINF` / `np.NINF` in preparation for NumPy 2.0.0 release. 
   By :user:`Joe Hamman <jhamman>` :issue:`1842`.
 
 Deprecations

pyproject.toml

@@ -10,7 +10,7 @@ readme = { file = "README.md", content-type = "text/markdown" }
 maintainers = [
     { name = "Alistair Miles", email = "alimanfoo@googlemail.com" }
 ]
-requires-python = ">=3.10"
+requires-python = ">=3.9"
 dependencies = [
     'asciitree',
     'numpy>=1.23',
@@ -30,9 +30,9 @@ classifiers = [
     'Topic :: Software Development :: Libraries :: Python Modules',
     'Operating System :: Unix',
     'Programming Language :: Python :: 3',
+    'Programming Language :: Python :: 3.9',
     'Programming Language :: Python :: 3.10',
     'Programming Language :: Python :: 3.11',
-    'Programming Language :: Python :: 3.12',
 ]
 license = { text = "MIT" }