在python中访问指向结构的c指针

Question

是否可以将int强制转换为类类型?

我有以下C代码:

#include "Python.h"
#define PYTHON_FILENAME "modelparam"
void getmodelparam(long pModelParam) ;
typedef struct {
 int seconds;
 int nanoseconds;
} someTime;

int main ()
{
someTime *pSome ;
long a ;
printf ("Testing the python interfacesn") ;
pSome = (someTime *) calloc(1, sizeof(someTime)) ;
pSome->seconds = 10 ;
pSome->nanoseconds = 20 ;
a = (long) pSome ;
printf ("a is %d, pSome is %dn", a, pSome) ;
getmodelparam(a) ;  
printf ("After the python call values are : %d, %dn",pSome->seconds, pSome->nanoseconds) ; 
return 0 ;
}
void getmodelparam(long pModelParam)
{
    PyObject    *pName ;
PyObject    *pModule ; 
PyObject    *pDict ;
PyObject    *pFunc ;
int         iSize = 0 ;
char        pcFunctionName[] = "modifymodelparam" ;
double      dTemp1, dTemp2 ; 
/* Initialize the python interpreter */
Py_Initialize() ;
/* Get Python code/module */
pName = PyUnicode_FromString(PYTHON_FILENAME);
if (NULL != pName)
{
    /* Import the module equivalent to doing 'import calresidual' in python */
    pModule = PyImport_Import(pName);
    Py_DECREF(pName) ;
    if (NULL != pModule)
    {
        /* Get the function and check if its callable function */   
        pFunc = PyObject_GetAttrString(pModule, pcFunctionName);
        if (pFunc && PyCallable_Check(pFunc))
        {
            /* Build the input arguments */
            PyObject *pResult = PyObject_CallFunction(pFunc,"i", pModelParam) ;
        }
        else
        {
            printf ("Some error with the functionn") ;
        }
    }
    else
    {
        printf ("Couldnt load the module %sn", PYTHON_FILENAME) ;
    }
}
else
{
    printf ("Couldnt convert the name of the module to python namen") ;
}
/* Release the resources. */
Py_DECREF(pModule) ;
Py_DECREF(pFunc) ;
Py_DECREF(pName) ;
/*Release the interpreter */
Py_Finalize() ;
}

在Python代码中:

import ctypes
class someTime(ctypes.Structure):
     _fields_ = [("seconds", ctypes.c_uint),
                 ("nanoseconds", ctypes.c_uint)]  
def modifymodelparam(m):
# Not sure how to access internal elements using m ?? 
    # How to typecast m ?? 
    n = someTime(m)
print ('Seconds', n.seconds)

如何将从C传递的地址类型转换为Python中的类类型，以便我可以访问这些类参数或间接访问结构参数?

Answer 1

上面的代码有一些错误。

需要将指针地址作为unsigned long/int类型传递给python模块。所以

void getmodelparam(long pModelParam)
//has to become
void getmodelparam(unsigned long pModelParam)
//and 
PyObject *pResult = PyObject_CallFunction(pFunc,"i", pModelParam) ;
// has to become 
PyObject *pResult = PyObject_CallFunction(pFunc,"k", pModelParam) ;

然后在python文件中:

def modifymodelparam(m):
    n = ctypes.cast(m, ctypes.POINTER(someTime))
    print (n.contents.seconds)
    print (n.contents.nanoseconds)

Answer 2

要进行类型转换，可以使用强制转换函数

n = ctypes。铸型(m,有时)

[谷歌]http://docs.python.org/2/library/ctypes.html