Add Python 3.13 support with upper version cap

Add 3.13 to build matrices (publish.yml), CI test matrix (rust-test.yml),
classifiers (pyproject.toml), and docs (README.md). Cap requires-python
at <3.14 to prevent broken installs on untested versions.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: igerber

.github/workflows/publish.yml

@@ -22,7 +22,7 @@ jobs:
       - name: Build wheels
         run: |
           export PATH="$HOME/.cargo/bin:$PATH"
-          for pyver in 39 310 311 312; do
+          for pyver in 39 310 311 312 313; do
             pybin="/opt/python/cp${pyver}-cp${pyver}/bin/python"
             if [ -f "$pybin" ]; then
               /opt/python/cp312-cp312/bin/maturin build --release --out dist -i "$pybin" --features extension-module
@@ -42,7 +42,7 @@ jobs:
     runs-on: macos-14
     strategy:
       matrix:
-        python-version: ['3.9', '3.10', '3.11', '3.12']
+        python-version: ['3.9', '3.10', '3.11', '3.12', '3.13']
     steps:
       - uses: actions/checkout@v4
 
@@ -72,7 +72,7 @@ jobs:
     runs-on: windows-latest
     strategy:
       matrix:
-        python-version: ['3.9', '3.10', '3.11', '3.12']
+        python-version: ['3.9', '3.10', '3.11', '3.12', '3.13']
     steps:
       - uses: actions/checkout@v4
 

.github/workflows/rust-test.yml

@@ -45,25 +45,27 @@ jobs:
 
   # Build and test with Python on multiple platforms
   python-tests:
-    name: Python Tests (${{ matrix.os }})
+    name: Python Tests (${{ matrix.os }}, py${{ matrix.python-version }})
     runs-on: ${{ matrix.os }}
     strategy:
       fail-fast: false
       matrix:
         os: [ubuntu-latest, macos-latest, windows-latest]
+        python-version: ['3.11', '3.13']
 
     steps:
       - uses: actions/checkout@v4
 
       - name: Set up Python
         uses: actions/setup-python@v5
         with:
-          python-version: '3.11'
+          python-version: ${{ matrix.python-version }}
 
       - name: Install Rust toolchain
         uses: dtolnay/rust-toolchain@stable
 
       - name: Install test dependencies
+        # Keep in sync with pyproject.toml [project.dependencies] and [project.optional-dependencies.dev]
         run: pip install pytest pytest-xdist numpy pandas scipy
 
       - name: Build and install with maturin
@@ -141,9 +143,10 @@ jobs:
       - name: Set up Python
         uses: actions/setup-python@v5
         with:
-          python-version: '3.11'
+          python-version: '3.13'
 
       - name: Install dependencies
+        # Keep in sync with pyproject.toml [project.dependencies] and [project.optional-dependencies.dev]
         run: pip install numpy pandas scipy pytest pytest-xdist
 
       - name: Verify pure Python mode

README.md

@@ -2452,7 +2452,7 @@ Returns DataFrame with columns: `unit`, `quality_score`, `outcome_trend_score`,
 
 ## Requirements
 
-- Python >= 3.9
+- Python 3.9 - 3.13
 - numpy >= 1.20
 - pandas >= 1.3
 - scipy >= 1.7

pyproject.toml

@@ -8,7 +8,7 @@ version = "2.3.1"
 description = "A library for Difference-in-Differences causal inference analysis"
 readme = "README.md"
 license = "MIT"
-requires-python = ">=3.9"
+requires-python = ">=3.9,<3.14"
 authors = [
     {name = "diff-diff contributors"}
 ]
@@ -28,6 +28,7 @@ classifiers = [
     "Programming Language :: Python :: 3.10",
     "Programming Language :: Python :: 3.11",
     "Programming Language :: Python :: 3.12",
+    "Programming Language :: Python :: 3.13",
     "Topic :: Scientific/Engineering :: Mathematics",
 ]
 dependencies = [