如何在python中从C结构体到int进行c++映射

How to make a C++ mapping from C struct to int in cython?

本文关键字：int 进行 c++ 映射 结构体 python 中从      更新时间：2023-10-16

如何在cython中从C结构到int进行c++映射?

我尝试下面的代码:

main.py 

#!/usr/bin/env python
# encoding: utf-8
import pyximport

pyximport.install()
from foo import Fun
Fun()

foo.pyx 

#!/usr/bin/env python
# encoding: utf-8
from libcpp.map cimport map
from libcpp.string cimport string
cdef struct mystruct:
    int i

def Fun():
    cdef:
        map[mystruct,int] dDict
        mystruct A
    A.i=1
    dDict[A]=1

配置文件foo.pyxbld

def make_ext(modname, pyxfilename):
    from distutils.extension import Extension
    return Extension(name=modname,
                     sources=[pyxfilename],
                     language='C++')
当运行main.py时，我得到以下错误: 
foo.cpp
C:Program Files (x86)Microsoft Visual Studio 9.0VCINCLUDExlocale(342) : warning C4530: C++ exception handler used, but unwind semantics are not enabled. Specify /EHsc
C:Program Files (x86)Microsoft Visual Studio 9.0VCINCLUDEfunctional(143) : error C2784: 'bool std::operator <(const std::basic_string<_Elem,_Traits,_Alloc> &,const _Elem *)' : could not deduce template argument for 'const std::basic_string<_Elem,_Traits,_Alloc> &' from 'const __pyx_t_3foo_mystruct'
        C:Program Files (x86)Microsoft Visual Studio 9.0VCINCLUDEstring(150) : see declaration of 'std::operator <'
        C:Program Files (x86)Microsoft Visual Studio 9.0VCINCLUDEfunctional(142) : while compiling class template member function 'bool std::less<_Ty>::operator ()(const _Ty &,const _Ty &) const'
        with
        [
            _Ty=__pyx_t_3foo_mystruct
        ]
        C:Program Files (x86)Microsoft Visual Studio 9.0VCINCLUDEmap(68) : see reference to class template instantiation 'std::less<_Ty>' being compiled
        with
        [
            _Ty=__pyx_t_3foo_mystruct
        ]
        C:Program Files (x86)Microsoft Visual Studio 9.0VCINCLUDExtree(22) : see reference to class template instantiation 'std::_Tmap_traits<_Kty,_Ty,_Pr,_Alloc,_Mfl>' being compiled
        with
        [
            _Kty=__pyx_t_3foo_mystruct,
            _Ty=int,
            _Pr=std::less<__pyx_t_3foo_mystruct>,
            _Alloc=std::allocator<std::pair<const __pyx_t_3foo_mystruct,int>>,
            _Mfl=false
        ]
        C:Program Files (x86)Microsoft Visual Studio 9.0VCINCLUDExtree(63) : see reference to class template instantiation 'std::_Tree_nod<_Traits>' being compiled
        with
        [
            _Traits=std::_Tmap_traits<__pyx_t_3foo_mystruct,int,std::less<__pyx_t_3foo_mystruct>,std::allocator<std::pair<const __pyx_t_3foo_mystruct,int>>,false>
        ]
        C:Program Files (x86)Microsoft Visual Studio 9.0VCINCLUDExtree(89) : see reference to class template instantiation 'std::_Tree_ptr<_Traits>' being compiled
        with
        [
            _Traits=std::_Tmap_traits<__pyx_t_3foo_mystruct,int,std::less<__pyx_t_3foo_mystruct>,std::al

我应该如何正确地初始化和使用这个映射?提前感谢您的帮助!

为了能够使用键类型为mystruct的映射，您需要为mystruct对象定义比较操作符。实际上，c++地图是有序的(通常由一些自动平衡树支持，如AVL或红黑)。正确的语法是

cdef cppclass mystruct:
    int i
    bint lessthan "operator<"(const mystruct t) const:
         return this.i < t.i

Edit:用this.i < t.i替换i < t.i，因为这更显式(Python的Zen)。

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