Drop Python 3.9 support (#6040)

Contributes to rapidsai/build-planning#88

Finishes the work of dropping Python 3.9 support.

This project stopped building / testing against Python 3.9 as of rapidsai/shared-workflows#235.
This PR updates configuration and docs to reflect that.

## Notes for Reviewers

### How I tested this

Checked that there were no remaining uses like this:

```shell
git grep -E '3\.9'
git grep '39'
git grep 'py39'
```

And similar for variations on Python 3.8 (to catch things that were missed the last time this was done).

Authors:
  - James Lamb (https://github.com/jameslamb)

Approvers:
  - Bradley Dice (https://github.com/bdice)

URL: #6040

conda/environments/all_cuda-118_arch-x86_64.yaml

@@ -57,7 +57,7 @@ dependencies:
 - pytest-cov
 - pytest-xdist
 - pytest==7.*
-- python>=3.9,<3.12
+- python>=3.10,<3.12
 - raft-dask==24.10.*,>=0.0.0a0
 - rapids-build-backend>=0.3.0,<0.4.0.dev0
 - rapids-dask-dependency==24.10.*,>=0.0.0a0

conda/environments/all_cuda-125_arch-x86_64.yaml

@@ -53,7 +53,7 @@ dependencies:
 - pytest-cov
 - pytest-xdist
 - pytest==7.*
-- python>=3.9,<3.12
+- python>=3.10,<3.12
 - raft-dask==24.10.*,>=0.0.0a0
 - rapids-build-backend>=0.3.0,<0.4.0.dev0
 - rapids-dask-dependency==24.10.*,>=0.0.0a0

dependencies.yaml

@@ -462,10 +462,6 @@ dependencies:
     specific:
       - output_types: conda
         matrices:
-          - matrix:
-              py: "3.9"
-            packages:
-              - python=3.9
           - matrix:
               py: "3.10"
             packages:
@@ -476,7 +472,7 @@ dependencies:
               - python=3.11
           - matrix:
             packages:
-              - python>=3.9,<3.12
+              - python>=3.10,<3.12
   test_libcuml:
     common:
       - output_types: conda

python/cuml/cuml/internals/available_devices.py

@@ -1,5 +1,5 @@
 #
-# Copyright (c) 2022-2023, NVIDIA CORPORATION.
+# Copyright (c) 2022-2024, NVIDIA CORPORATION.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -16,12 +16,8 @@
 from cuml.internals.device_support import GPU_ENABLED
 from cuml.internals.safe_imports import gpu_only_import_from, UnavailableError
 
-try:
-    from functools import cache  # requires Python >= 3.9
-except ImportError:
-    from functools import lru_cache
 
-    cache = lru_cache(maxsize=None)
+from functools import cache
 
 
 def gpu_available_no_context_creation():

python/cuml/pyproject.toml

@@ -78,7 +78,7 @@ authors = [
     { name = "NVIDIA Corporation" },
 ]
 license = { text = "Apache 2.0" }
-requires-python = ">=3.9"
+requires-python = ">=3.10"
 dependencies = [
     "cudf==24.10.*,>=0.0.0a0",
     "cupy-cuda11x>=12.0.0",
@@ -102,7 +102,6 @@ dependencies = [
 classifiers = [
     "Intended Audience :: Developers",
     "Programming Language :: Python",
-    "Programming Language :: Python :: 3.9",
     "Programming Language :: Python :: 3.10",
     "Programming Language :: Python :: 3.11",
 ]
@@ -134,7 +133,7 @@ Documentation = "https://docs.rapids.ai/api/cuml/stable/"
 
 [tool.black]
 line-length = 79
-target-version = ["py39"]
+target-version = ["py310"]
 include = '\.py?$'
 force-exclude = '''
 _stop_words\.py |