使用 Cython 将 Python 链接到共享库

2022-01-11 00:00:00 python distutils cython c linker

问题描述

我正在尝试使用 Cython 将用 C 编写的第三方库与我的 python 应用程序集成.我已经为测试编写了所有 python 代码.我无法找到设置此示例的示例.

I am trying to integrate a third party library written in C with my python application using Cython. I have all of the python code written for a test. I am having trouble finding an example for setting this up.

我有一个手动创建的 pyd/pyx 文件.第三方给了我一个头文件(*.h)和一个共享库(*.so).据我所知，没有其他依赖项.有人可以提供一个如何使用 Cython 和 disutils 进行设置的示例吗?

I have a pyd/pyx file I created manually. The third party has given me a header file (*.h) and a shared library (*.so). As far as I can tell, there are no other dependencies. Can someone provide an example of how to set this up using Cython and disutils?

谢谢

解决方案

好的！

(以下，我假设你已经知道如何处理cimport以及.pxd和.pyx之间的交互.如果情况不完全如此，请询问，我也会开发该部分)

(In the following, I assume that you already know how to deal with cimport and the interactions between .pxd and .pyx. If this is not completely the case, just ask and I will develop that part as well)

示例(从我的 C++ 项目中获取，但 C 项目的工作方式几乎相同):

The sample (grabbed from a C++ project of mine, but a C project would work pretty much the same) :

1.Distutils 安装文件:

假设要创建的扩展名为myext，第三方共享库为libexternlib.so(注意lib*前缀，这里)...

Assuming that the extension to be created will be called myext and the 3rd party shared library is libexternlib.so (note the lib* prefix, here)...

# setup.py file
import sys
import os
import shutil

from distutils.core import setup
from distutils.extension import Extension
from Cython.Distutils import build_ext

# clean previous build
for root, dirs, files in os.walk(".", topdown=False):
    for name in files:
        if (name.startswith("myext") and not(name.endswith(".pyx") or name.endswith(".pxd"))):
            os.remove(os.path.join(root, name))
    for name in dirs:
        if (name == "build"):
            shutil.rmtree(name)

# build "myext.so" python extension to be added to "PYTHONPATH" afterwards...
setup(
    cmdclass = {'build_ext': build_ext},
    ext_modules = [
        Extension("myext", 
                  sources=["myext.pyx",
                           "SomeAdditionalCppClass1.cpp",
                           "SomeAdditionalCppClass2.cpp"
                       ],
                  libraries=["externlib"],          # refers to "libexternlib.so"
                  language="c++",                   # remove this if C and not C++
                  extra_compile_args=["-fopenmp", "-O3"],
                  extra_link_args=["-DSOME_DEFINE_OPT", 
                                   "-L./some/extra/dependency/dir/"]
             )
        ]
)

注意:您的外部 .so 文件通过 libraries 选项链接:

Note : Your external .so file is linked via the libraries option :

libraries=["externlib"]   # Without the 'lib' prefix and the '.so' extension...

注意:sources 选项可用于编译一些额外的源文件.

Note : the sources option can be used to get some additional source files compiled.

重要: myext.pxd(不要与 .pyd - Windows 的东西混淆)和 myext.pyx 应该在同一目录中.在编译时，首先处理定义文件(如果存在)(more).

Important : myext.pxd (do not confound with .pyd - Windows stuff) and myext.pyx should be in the same directory. At compile time the definition file, if it exists, is processed first (more).

<强>2.然后运行如下:

将目录更改为包含您的 myext.pxd、您的 myext.pyx 以及上述 setup.py 的目录后脚本:

After having changed directory to the one containing your myext.pxd, your myext.pyx, as well as the above setup.py script :

# setup.sh
# Make the "myext" Python Module ("myext.so")
CC="gcc"   
CXX="g++"   
CFLAGS="-I./some/path/to/includes/ -I../../../DEPENDENCIES/python2.7/inc -I../../../DEPENDENCIES/gsl-1.15"   
LDFLAGS="-L./some/path/to/externlib/"   
    python setup.py build_ext --inplace

地点:

  • libexternlib.so 假定位于 ./some/path/to/externlib/
  • yourheader.h 假定位于 ./some/path/to/includes/
  • libexternlib.so is assumed to be located at ./some/path/to/externlib/
  • yourheader.h is assumed to be located at ./some/path/to/includes/

注意:CFLAGS 也可以使用 extra_compile_args 选项进行设置:

Note : CFLAGS could also have been setup using the extra_compile_args option :

extra_compile_args=["-I./some/path/to/includes/", "-fopenmp", "-O3"]

注意:LDFLAGS 也可以使用 extra_link_args 选项进行设置:

Note : LDFLAGS could also have been setup using the extra_link_args option :

extra_link_args=["-L./some/path/to/externlib/", "-DSOME_DEFINE_OPT", "-L./some/extra/dependency/dir/"]

distutils 构建完成后，您会得到一些新文件，特别是 myext.cpp、myext.h，最重要的是 myext.所以.

Once distutils is done with the build, you get some new files, specially the myext.cpp, myext.h and most importantly, the myext.so.

3.之后，您就可以开始了:

export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:./some/path/to/externlib/
export PYTHONPATH=$PYTHONPATH:./some/path/to/myext/

# Run some script requiring "myext.so"
python somescript.py

您新创建的 Python 扩展可以通过其名称导入:

Where your freshly created Python extension can be imported by its name :

# somescript.py
import myext
from myext import PySomeFeature
...

注意关于优化:默认情况下 -O2 用于编译扩展，但这可以重载(参见上面的设置 -O3 已指定).

Note about Optimization : By default -O2 is used for compiling the extension, but this can be overloaded (see above setup where -O3 is specified).

注意关于 Cython 路径:如果 Cython 安装在自定义目录中，您可能需要先将其添加到您的环境中:

Note about Cython paths : If Cython was installed in a custom directory, you might want to add it to your environment, before all :

PYTHONPATH=$PYTHONPATH:../../../DEPENDENCIES/Cython-0.18 export PYTHONPATH;
PATH=$PATH:../../../DEPENDENCIES/Cython-0.18/bin; export PATH;

嗯，希望我能讲到要点……

Well, hope I covered the main points...

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