[python-package] drop Python 3.6 support, add Python 3.12 (#6459)

.ci/conda-envs/ci-core-py38.txt

+# [description]
+#
+#   Similar to ci-core.txt, but specific to Python 3.8.
+#
+#   Unlike ci-core.txt, this includes a Python version and uses
+#   `=` and `<=` pins to make solves faster and prevent against
+#   issues like https://github.com/microsoft/LightGBM/pull/6370.
+#
+# [usage]
+#
+#   conda create \
+#     --name test-env \
+#     --file ./.ci/conda-envs/ci-core-py38.txt
+#
+
+# python
+python=3.8.*
+
+# direct imports
+cffi=1.15.*
+dask=2023.5.*
+distributed=2023.5.*
+joblib=1.4.*
+matplotlib-base=3.7.*
+numpy=1.24.*
+pandas=1.5.*
+pyarrow-core=16.1.*
+python-graphviz=0.20.*
+scikit-learn=1.3.*
+scipy=1.10.*
+
+# testing-only dependencies
+cloudpickle=3.0.*
+pluggy=1.5.*
+psutil=5.9.8
+pytest=8.2.*
+
+# other recursive dependencies, just
+# pinned here to help speed up solves
+bokeh=3.1.*
+fsspec=2024.5.*
+msgpack-python=1.0.*
+pluggy=1.5.*
+pytz=2024.1
+setuptools=69.5.*
+snappy=1.2.*
+tomli=2.0.*
+tornado=6.4.*
+wheel=0.43.*
+zict=3.0.*
+zipp=3.17.*

.ci/test-python-oldest.sh

@@ -3,19 +3,20 @@
 set -e -E -u -o pipefail
 
 # oldest versions of dependencies published after
-# minimum supported Python version's first release
+# minimum supported Python version's first release,
+# for which there are wheels compatible with the
+# python:{version} image
 #
 # see https://devguide.python.org/versions/
 #
 echo "installing lightgbm's dependencies"
 pip install \
   'cffi==1.15.1' \
-  'dataclasses' \
-  'numpy==1.16.6' \
-  'pandas==0.24.0' \
+  'numpy==1.19.0' \
+  'pandas==1.1.3' \
   'pyarrow==6.0.1' \
-  'scikit-learn==0.18.2' \
-  'scipy==0.19.0' \
+  'scikit-learn==0.24.0' \
+  'scipy==1.6.0' \
 || exit 1
 echo "done installing lightgbm's dependencies"
 

.ci/test.sh

@@ -132,6 +132,8 @@ fi
 
 if [[ $PYTHON_VERSION == "3.7" ]]; then
     CONDA_REQUIREMENT_FILES="--file ${BUILD_DIRECTORY}/.ci/conda-envs/ci-core-py37.txt"
+elif [[ $PYTHON_VERSION == "3.8" ]]; then
+    CONDA_REQUIREMENT_FILES="--file ${BUILD_DIRECTORY}/.ci/conda-envs/ci-core-py38.txt"
 else
     CONDA_REQUIREMENT_FILES="--file ${BUILD_DIRECTORY}/.ci/conda-envs/ci-core.txt"
 fi

.ci/test_windows.ps1

@@ -55,6 +55,8 @@ conda update -q -y conda
 
 if ($env:PYTHON_VERSION -eq "3.7") {
   $env:CONDA_REQUIREMENT_FILE = "$env:BUILD_SOURCESDIRECTORY/.ci/conda-envs/ci-core-py37.txt"
+} elseif ($env:PYTHON_VERSION -eq "3.8") {
+  $env:CONDA_REQUIREMENT_FILE = "$env:BUILD_SOURCESDIRECTORY/.ci/conda-envs/ci-core-py38.txt"
 } else {
   $env:CONDA_REQUIREMENT_FILE = "$env:BUILD_SOURCESDIRECTORY/.ci/conda-envs/ci-core.txt"
 }

.github/workflows/cuda.yml

@@ -82,19 +82,19 @@ jobs:
         include:
           - method: wheel
             compiler: gcc
-            python_version: "3.11"
+            python_version: "3.10"
             cuda_version: "11.8.0"
             image: nvcr.io/nvidia/cuda:11.8.0-devel-ubuntu20.04
             task: cuda
           - method: source
             compiler: gcc
-            python_version: "3.9"
+            python_version: "3.12"
             cuda_version: "12.2.0"
             image: nvcr.io/nvidia/cuda:12.2.0-devel-ubuntu22.04
             task: cuda
           - method: pip
             compiler: clang
-            python_version: "3.10"
+            python_version: "3.11"
             cuda_version: "11.8.0"
             image: nvcr.io/nvidia/cuda:11.8.0-devel-ubuntu20.04
             task: cuda

.github/workflows/linkchecker.yml

@@ -10,7 +10,7 @@ on:
 env:
   CONDA_ENV: test-env
   OS_NAME: 'linux'
-  PYTHON_VERSION: '3.11'
+  PYTHON_VERSION: '3.12'
   TASK: 'check-links'
 
 jobs:

.github/workflows/python_package.yml

@@ -29,30 +29,30 @@ jobs:
         include:
           - os: macos-13
             task: regular
-            python_version: '3.9'
+            python_version: '3.10'
           - os: macos-13
             task: sdist
-            python_version: '3.10'
+            python_version: '3.11'
           - os: macos-13
             task: bdist
-            python_version: '3.7'
+            python_version: '3.8'
           - os: macos-13
             task: if-else
-            python_version: '3.9'
+            python_version: '3.10'
           # We're currently skipping MPI jobs on macOS, see https://github.com/microsoft/LightGBM/pull/6425
           # for further details.
           # - os: macos-13
           #   task: mpi
           #   method: source
-          #   python_version: '3.10'
+          #   python_version: '3.11'
           # - os: macos-13
           #   task: mpi
           #   method: pip
-          #   python_version: '3.11'
+          #   python_version: '3.12'
           # - os: macos-13
           #   task: mpi
           #   method: wheel
-          #   python_version: '3.8'
+          #   python_version: '3.9'
     steps:
       - name: Checkout repository
         uses: actions/checkout@v4
@@ -101,7 +101,7 @@ jobs:
             --rm \
             -v $(pwd):/opt/lgb-build \
             -w /opt/lgb-build \
-            python:3.6 \
+            python:3.7 \
             /bin/bash ./.ci/test-python-oldest.sh
   all-python-package-jobs-successful:
     if: always()

.github/workflows/static_analysis.yml

@@ -20,7 +20,7 @@ env:
   COMPILER: 'gcc'
   CONDA_ENV: test-env
   OS_NAME: 'linux'
-  PYTHON_VERSION: '3.11'
+  PYTHON_VERSION: '3.12'
 
 jobs:
   test:

.vsts-ci.yml

@@ -10,8 +10,8 @@ pr:
 - release/*
 variables:
   AZURE: 'true'
-  PYTHON_VERSION: '3.11'
   CMAKE_BUILD_PARALLEL_LEVEL: 4
+  PYTHON_VERSION: '3.12'
   CONDA_ENV: test-env
   runCodesignValidationInjection: false
   skipComponentGovernanceDetection: true
@@ -62,19 +62,19 @@ jobs:
     matrix:
       regular:
         TASK: regular
-        PYTHON_VERSION: '3.9'
+        PYTHON_VERSION: '3.10'
       sdist:
         TASK: sdist
-        PYTHON_VERSION: '3.7'
+        PYTHON_VERSION: '3.8'
       bdist:
         TASK: bdist
-        PYTHON_VERSION: '3.8'
+        PYTHON_VERSION: '3.9'
       inference:
         TASK: if-else
       mpi_source:
         TASK: mpi
         METHOD: source
-        PYTHON_VERSION: '3.8'
+        PYTHON_VERSION: '3.9'
       gpu_source:
         TASK: gpu
         METHOD: source
@@ -127,7 +127,7 @@ jobs:
         TASK: sdist
       bdist:
         TASK: bdist
-        PYTHON_VERSION: '3.9'
+        PYTHON_VERSION: '3.10'
       inference:
         TASK: if-else
       mpi_source:
@@ -136,23 +136,23 @@ jobs:
       mpi_pip:
         TASK: mpi
         METHOD: pip
-        PYTHON_VERSION: '3.10'
+        PYTHON_VERSION: '3.11'
       mpi_wheel:
         TASK: mpi
         METHOD: wheel
-        PYTHON_VERSION: '3.8'
+        PYTHON_VERSION: '3.9'
       gpu_source:
         TASK: gpu
         METHOD: source
-        PYTHON_VERSION: '3.10'
+        PYTHON_VERSION: '3.11'
       gpu_pip:
         TASK: gpu
         METHOD: pip
-        PYTHON_VERSION: '3.9'
+        PYTHON_VERSION: '3.10'
       gpu_wheel:
         TASK: gpu
         METHOD: wheel
-        PYTHON_VERSION: '3.8'
+        PYTHON_VERSION: '3.9'
       cpp_tests:
         TASK: cpp-tests
         METHOD: with-sanitizers

python-package/pyproject.toml

@@ -15,10 +15,10 @@ classifiers = [
     "Programming Language :: Python :: 3.9",
     "Programming Language :: Python :: 3.10",
     "Programming Language :: Python :: 3.11",
+    "Programming Language :: Python :: 3.12",
     "Topic :: Scientific/Engineering :: Artificial Intelligence"
 ]
 dependencies = [
-    "dataclasses ; python_version < '3.7'",
     "numpy",
     "scipy"
 ]
@@ -29,7 +29,7 @@ maintainers = [
 ]
 name = "lightgbm"
 readme = "README.rst"
-requires-python = ">=3.6"
+requires-python = ">=3.7"
 version = "4.3.0.99"
 
 [project.optional-dependencies]