如何通过Bazel使用独立Python环境构建简易pybind库？

问题说明 #

我正在搭建简易Bazel工作区构建pybind扩展库，希望通过rules_python拉取特定版本的Python（而非系统默认Python），但配置遇到阻碍：

• 移除WORKSPACE中python_configure规则的python_interpreter_target参数时，构建可正常运行，但会使用系统Python；
• 查询@python3_9的所有目标后，仍无法确定python_interpreter_target的正确取值。

目录结构 #

.
├── BUILD
├── WORKSPACE
└── example.cpp

BUILD文件内容 #

load("@pybind11_bazel//:build_defs.bzl", "pybind_extension")

pybind_extension(
    name = "example",
    srcs = ["example.cpp"],
    deps = [ ],
)

WORKSPACE文件内容 #

load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
http_archive(
    name = "rules_python",
    sha256 = "8c8fe44ef0a9afc256d1e75ad5f448bb59b81aba149b8958f02f7b3a98f5d9b4",
    strip_prefix = "rules_python-0.13.0",
    url = "https://github.com/bazelbuild/rules_python/archive/refs/tags/0.13.0.tar.gz",
)

load("@rules_python//python:repositories.bzl", "python_register_toolchains")

python_register_toolchains(
    name = "python3_9",
    python_version = "3.9",
)

load("@python3_9//:defs.bzl", "interpreter")

load("@rules_python//python:pip.bzl", "pip_parse")

pip_parse(
    python_interpreter_target = interpreter,
)

http_archive(
  name = "pybind11_bazel",
  strip_prefix = "pybind11_bazel-9a24c33cbdc510fa60ab7f5ffb7d80ab89272799",
  urls = ["https://github.com/pybind/pybind11_bazel/archive/9a24c33cbdc510fa60ab7f5ffb7d80ab89272799.zip"],
)
http_archive(
  name = "pybind11",
  build_file = "@pybind11_bazel//:pybind11.BUILD",
  strip_prefix = "pybind11-2.10.0",
  urls = ["https://github.com/pybind/pybind11/archive/refs/tags/v2.10.0.zip"],
)
load("@pybind11_bazel//:python_configure.bzl", "python_configure")
python_configure(
  name = "local_config_python",
  python_interpreter_target = "**what goes here**",
)

example.cpp文件内容 #

#include <pybind11/pybind11.h>

namespace py = pybind11;

void do_something() { }

PYBIND11_MODULE(example, m) {
    m.def("do_something", &do_something, "A function that does something");
}

查询@python3_9目标结果 #

% bazel query @python3_9//... 
@python3_9//:files
@python3_9//:includes
@python3_9//:libpython
@python3_9//:pip
@python3_9//:py3_runtime
@python3_9//:python3
@python3_9//:python_headers
@python3_9//:python_runtimes
Loading: 0 packages loaded

解决方案 #

核心问题是**python_configure是旧版Python配置规则，与rules_python的toolchain机制不兼容**，无需纠结python_interpreter_target的取值，直接移除旧规则并配置toolchain即可：

1. 清理WORKSPACE中的旧规则
   删除以下内容：

   load("@pybind11_bazel//:python_configure.bzl", "python_configure")
   python_configure(
     name = "local_config_python",
     python_interpreter_target = "**what goes here**",
   )
   

2. 配置使用指定的Python toolchain
   在项目根目录创建或修改.bazelrc文件，添加以下配置：

   build --python_version=3.9
   build --toolchain=@python3_9//:py3_runtime
   

   这条配置会全局指定Bazel使用@python3_9注册的Python 3.9版本进行构建。

3. 验证构建
   重新执行构建命令，此时Bazel会使用rules_python拉取的Python 3.9，而非系统Python。

补充说明：@python3_9//:python3就是对应拉取的Python解释器目标，但由于python_configure属于旧规则体系，和新的toolchain无法协同工作，因此直接弃用旧规则是最简洁的解决方案。

内容的提问来源于stack exchange，提问作者digitalPhonix