python - 有没有办法在 Python 和 C 之间传递结构

Question

我正在使用 Python API 用 C 编写程序。

Python 将输入(结构)传递给 C 程序，C 程序将根据输入执行一些操作。

谁能告诉我是否可以在 Python 和 C 之间传递结构。如果可以，请告诉我如何传递它。

我使用 SWIG 接口(interface)在 C 和 Python 之间传递值。示例程序运行良好(使用变量)。我已经添加了带有结构的代码，但我不确定它的代码格式。如果我做错了什么，请纠正我。我是 Python 和 C 的新手。我到处搜索使用 SWIG 传递结构，但没有得到任何正确答案。

逻辑是从Python中获取输入值并在c中执行乘法运算并将值返回给Python。

Sample.c
#include<stdio.h>
#include "sample.h"

struct info sample;

int getstruct (struct info sample);

int getstruct (struct info sample) {

   int i = 0;
   int j = 0;
   int k = 0;
   int l = 0;

   i = 2 * sample.i;
   j = 2 * sample.j;
   k = 2 * sample.k;
   l = 2 * sample.l;

   sample.i = i;
   sample.j = j;
   sample.k = k;
   sample.l = l;

   return(&sample);

}

sample.h
struct info
{
   int i;
   int j;
   int k;
   int l;
};

extern struct info data;

sample.i
%module sample
%{
#include "sample.h"
%}

%include "sample.h"

sample.py (automatically generated by SWIG)
# This file was automatically generated by SWIG (http://www.swig.org).
# Version 2.0.11
#
# Do not make changes to this file unless you know what you are doing--modify
# the SWIG interface file instead.





from sys import version_info
if version_info >= (2,6,0):
    def swig_import_helper():
        from os.path import dirname
        import imp
        fp = None
        try:
            fp, pathname, description = imp.find_module('_sample', [dirname(__file__)])
        except ImportError:
            import _sample
            return _sample
        if fp is not None:
            try:
                _mod = imp.load_module('_sample', fp, pathname, description)
            finally:
                fp.close()
            return _mod
    _sample = swig_import_helper()
    del swig_import_helper
else:
    import _sample
del version_info
try:
    _swig_property = property
except NameError:
    pass # Python < 2.2 doesn't have 'property'.
def _swig_setattr_nondynamic(self,class_type,name,value,static=1):
    if (name == "thisown"): return self.this.own(value)
    if (name == "this"):
        if type(value).__name__ == 'SwigPyObject':
            self.__dict__[name] = value
            return
    method = class_type.__swig_setmethods__.get(name,None)
    if method: return method(self,value)
    if (not static):
        self.__dict__[name] = value
    else:
        raise AttributeError("You cannot add attributes to %s" % self)

def _swig_setattr(self,class_type,name,value):
    return _swig_setattr_nondynamic(self,class_type,name,value,0)

def _swig_getattr(self,class_type,name):
    if (name == "thisown"): return self.this.own()
    method = class_type.__swig_getmethods__.get(name,None)
    if method: return method(self)
    raise AttributeError(name)

def _swig_repr(self):
    try: strthis = "proxy of " + self.this.__repr__()
    except: strthis = ""
    return "<%s.%s; %s >" % (self.__class__.__module__, self.__class__.__name__, strthis,)

try:
    _object = object
    _newclass = 1
except AttributeError:
    class _object : pass
    _newclass = 0


class info(_object):
    __swig_setmethods__ = {}
    __setattr__ = lambda self, name, value: _swig_setattr(self, info, name, value)
    __swig_getmethods__ = {}
    __getattr__ = lambda self, name: _swig_getattr(self, info, name)
    __repr__ = _swig_repr
    __swig_setmethods__["i"] = _sample.info_i_set
    __swig_getmethods__["i"] = _sample.info_i_get
    if _newclass:i = _swig_property(_sample.info_i_get, _sample.info_i_set)
    __swig_setmethods__["j"] = _sample.info_j_set
    __swig_getmethods__["j"] = _sample.info_j_get
    if _newclass:j = _swig_property(_sample.info_j_get, _sample.info_j_set)
    __swig_setmethods__["k"] = _sample.info_k_set
    __swig_getmethods__["k"] = _sample.info_k_get
    if _newclass:k = _swig_property(_sample.info_k_get, _sample.info_k_set)
    __swig_setmethods__["l"] = _sample.info_l_set
    __swig_getmethods__["l"] = _sample.info_l_get
    if _newclass:l = _swig_property(_sample.info_l_get, _sample.info_l_set)
    def __init__(self):
        this = _sample.new_info()
        try: self.this.append(this)
        except: self.this = this
    __swig_destroy__ = _sample.delete_info
    __del__ = lambda self : None;
info_swigregister = _sample.info_swigregister
info_swigregister(info)

# This file is compatible with both classic and new-style classes.

cvar = _sample.cvar


Error message:
Python 2.7.6 (default, Mar 22 2014, 22:59:56)
[GCC 4.8.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import sample
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "sample.py", line 28, in <module>
    _sample = swig_import_helper()
  File "sample.py", line 24, in swig_import_helper
    _mod = imp.load_module('_sample', fp, pathname, description)
ImportError: ./_sample.so: undefined symbol: data
>>>

Commands used:
swig -python sample.i
gcc -fPIC -c sample.c sample_wrap.c -I/usr/include/python2.7
ld -shared sample.o sample_wrap.o -o _sample.so

Answer 1

可以查看swig .

我自己使用它并且可以确认它工作得很好。查看tutorial以 Python 为例。

正在执行以下代码:

头文件:

#include<stdio.h>

typedef struct
{
   int i;
   int j;
   int k;
   int l;
} MyStruct;

extern MyStruct sample;

extern int getstruct (MyStruct sample);

C文件

#include "example.h"

int getstruct (MyStruct sample) {

   int i = 0;
   int j = 0;
   int k = 0;
   int l = 0;

   i = 2 * sample.i;
   j = 2 * sample.j;
   k = 2 * sample.k;
   l = 2 * sample.l;

   sample.i = i;
   sample.j = j;
   sample.k = k;
   sample.l = l;

   return(&sample);
}

接口(interface)文件:

%module example
%{
#include "example.h"
%}

%include "example.h"

编译和链接文件:

$ swig -python example.i
$ gcc -fPIC -c example.c example_wrap.c -I/usr/include/python2.7
$ gcc -lpython -shared example.o example_wrap.o -o _example.so

现在是 python:

>>> import example
>>> a = example.MyStruct
>>> dir(a)
['__class__', '__del__', '__delattr__', '__dict__', '__doc__', 
 '__format__', '__getattr__', '__getattribute__', '__hash__',
 '__init__', '__module__', '__new__', '__reduce__', '__reduce_ex__',
 '__repr__', '__setattr__', '__sizeof__', '__str__',
 '__subclasshook__', '__swig_destroy__', '__swig_getmethods__',
 '__swig_setmethods__', '__weakref__', 'i', 'j', 'k', 'l', 'this']
>>> a.i = 1
>>> a.j = 1
>>> a.k = 1
>>> a.l = 1
>>> example.getstruct(a)
1605330080

我不确定结果是什么(也许是样本地址？)。

PS:我看了 Lee Daniel Crocker 的回复，值得考虑。