使用 pybind11 嵌入 python。虚拟环境不工作

Question

我正在尝试制作一个简单的 c++ 应用程序，它使用 googletrans python 库翻译短语。所以我为此选择了 pybind11 来embed python。我也使用 cmake 进行代码配置。

当我使用全局 python 安装时一切正常，但是 我不明白如何使用 pybind 使用虚拟环境 以及设置正确 python 解释器、路径等的整个过程. 在 cmake 中很多。

我找到了这个 stackoverflow 线程：Embedding pybind11 with virtual environment

我像@ipa 一样设置了所有变量。 看看CMakeLists.txt 和main.cpp：

cmake_minimum_required(VERSION 3.15)
project("cpp_google_trans")

set(
    PYTHON_EXECUTABLE "${CMAKE_HOME_DIRECTORY}/venv/Scripts/python.exe"
    CACHE FILEPATH "python virtual environment executable")
message(STATUS "PYTHON_EXECUTABLE is now: ${PYTHON_EXECUTABLE}")    #DEBUG

set(ENV{PYTHONPATH} "${CMAKE_HOME_DIRECTORY}/venv/Lib/site-packages")
message(STATUS "ENV{PYTHONPATH} is now: $ENV{PYTHONPATH}")  #DEBUG

set(
    ENV{PATH}
    "${CMAKE_HOME_DIRECTORY}/venv/Scripts/;${CMAKE_HOME_DIRECTORY}/venv/Lib"
)
message(STATUS "PATH is now: $ENV{PATH}")   #DEBUG

add_subdirectory(pybind11)

add_executable(app main.cpp)
target_link_libraries(app PRIVATE pybind11::embed)

main.cpp:

#include <iostream>
#include <string>
#include <pybind11/embed.h>
namespace py = pybind11;

int main() {
    py::scoped_interpreter guard{};

    auto sys = py::module::import("sys");
    py::print("Hello, World from Python!");
    py::print(sys.attr("executable"));
    py::print(sys.attr("version"));

    system("set PATH");

    std::cin.get();

    // system("powershell");
    // I was looking at the environment variables in the powershell, but there wasn't any variables I set in CMakeLists.txt

    // Here I get abort() when trying to import googletrans package.
    // The package is installed in the venv virtual environment.
    // When the package is installed globally there isn't any problem.
    py::object Translator = py::module::import("googletrans").attr("Translator");
    py::object translator = Translator();

    std::cout << "C++ program here!\nTell a phrase you want to translate to english: ";
    std::string phrase;
    std::getline(std::cin, phrase);

    std::cout << "\n\nThe phrase in english means: ";
    std::cout << translator.attr("translate")(py::cast(&phrase)).attr("text").cast<std::string>();
}

查看 cmake 配置输出时，一切似乎都运行良好（而不是 PythonLibs 变量，我不知道如何更改）：

-- Building for: Visual Studio 16 2019
-- The C compiler identification is MSVC 19.22.27812.2
-- The CXX compiler identification is MSVC 19.22.27812.2
-- Check for working C compiler: C:/Program Files (x86)/Microsoft Visual Studio/2019/Preview/VC/Tools/MSVC/14.22.27812/bin/Hostx64/x64/cl.exe
-- Check for working C compiler: C:/Program Files (x86)/Microsoft Visual Studio/2019/Preview/VC/Tools/MSVC/14.22.27812/bin/Hostx64/x64/cl.exe -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: C:/Program Files (x86)/Microsoft Visual Studio/2019/Preview/VC/Tools/MSVC/14.22.27812/bin/Hostx64/x64/cl.exe
-- Check for working CXX compiler: C:/Program Files (x86)/Microsoft Visual Studio/2019/Preview/VC/Tools/MSVC/14.22.27812/bin/Hostx64/x64/cl.exe -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- PYTHON_EXECUTABLE is now: D:/dev/Pybind/cpp_google_trans2/venv/Scripts/python.exe
-- ENV{PYTHONPATH} is now: D:/dev/Pybind/cpp_google_trans2/venv/Lib/site-packages
-- PATH is now: D:/dev/Pybind/cpp_google_trans2/venv/Scripts/;D:/dev/Pybind/cpp_google_trans2/venv/Lib    
-- Found PythonInterp: D:/dev/Pybind/cpp_google_trans2/venv/Scripts/python.exe (found version "3.7.3")    
-- Found PythonLibs: D:/Programs/VisualStudio/Shared/Python37_64/libs/Python37.lib
-- pybind11 v2.3.dev1
-- Configuring done
-- Generating done
-- Build files have been written to: D:/dev/Pybind/cpp_google_trans2/build

我还尝试通过control panel>system and security>system>advanced system settings>advanced>environment variables 全局设置 PYTHON_EXECUTABLE 和 PATH 环境变量，但即使这样也无济于事。

我对 cmake、python 和 pybind11 还是很陌生，我知道我不知道很多东西。也许您在阅读此主题时已经注意到了这一点。 ;P

Answer 1

解决方案涉及两个部分。

将 virtualenv PYTHONPATH 编译到您的 C++ 程序中
在 CMake 中，这可以通过 target_compile_definitions 完成。自定义路径将作为预处理器宏提供。

target_compile_definitions(app PRIVATE -DCUSTOM_SYS_PATH="\"${CMAKE_HOME_DIRECTORY}/venv/Lib/site-packages\"")

立即启动解释器更新 Python sys.path。

这是特定于 pybind 的，但应该看起来像：

py::module sys = py::module::import("sys");
sys.attr("path").attr("insert")(1, CUSTOM_SYS_PATH);