使用 Ctypes 传递数组

Question

所以我的python程序是

from ctypes import *
import ctypes

number = [0,1,2]
testlib = cdll.LoadLibrary("./a.out")


testlib.init.argtypes = [ctypes.c_int]
testlib.init.restype = ctypes.c_double

#create an array of size 3
testlib.init(3)

#Loop to fill the array

#use AccessArray to preform an action on the array

而C部分是

#include <stdio.h>


double init(int size){
    double points[size];

    return points[0];
}

double fillarray(double value, double location){

    // i need to access 
}

double AccessArray(double value, double location){

    // i need to acess the array that is filled in the previous function
}

所以我需要做的是将一个数组从 python 部分传递给 C 函数，以某种方式将该数组在 C 中移动到另一个函数，我将在其中访问它以便处理它。

我被困住了，因为我想不出一种方法来移动 C 部分中的数组。

谁能教我怎么做？

Answer 1

你应该尝试这样的事情（在你的 C 代码中）：

#include <stdio.h>

double points[1000];//change 1000 for the maximum size for you
int sz = 0;

double init(int size){
    //verify size <= maximum size for the array
    for(int i=0;i<size;i++) {
        points[i] = 1;//change 1 for the init value for you
    }
    sz = size;
    return points[0];
}

double fillarray(double value, double location){
    //first verify 0 < location < sz
    points[(int)location] = value;    
}

double AccessArray(double value, double location){
    //first verify 0 < location < sz
    return points[(int)location];
}

这是一个非常简单的解决方案，但是如果您需要分配一个任意大小的数组，您应该研究使用malloc

Answer 2

也许是这样的？

$ cat Makefile

go: a.out
        ./c-double

a.out: c.c
        gcc -fpic -shared c.c -o a.out

zareason-dstromberg:~/src/outside-questions/c-double x86_64-pc-linux-gnu 27062 - above cmd done 2013 Fri Dec 27 11:03 AM

$ cat c.c
#include <stdio.h>
#include <malloc.h>


double *init(int size) {
    double *points;

    points = malloc(size * sizeof(double));

    return points;
}

double fill_array(double *points, int size) {
    int i;
    for (i=0; i < size; i++) {
        points[i] = (double) i;
    }

}

double access_array(double *points, int size) {
    // i need to access the array that is filled in the previous function
    int i;
    for (i=0; i < size; i++) {
        printf("%d: %f\n", i, points[i]);
    }
}
zareason-dstromberg:~/src/outside-questions/c-double x86_64-pc-linux-gnu 27062 - above cmd done 2013 Fri Dec 27 11:03 AM

$ cat c-double
#!/usr/local/cpython-3.3/bin/python

import ctypes

testlib = ctypes.cdll.LoadLibrary("./a.out")

testlib.init.argtypes = [ctypes.c_int]
testlib.init.restype = ctypes.c_void_p

#create an array of size 3
size = 3
double_array = testlib.init(size)

#Loop to fill the array
testlib.fill_array(double_array, size)

#use AccessArray to preform an action on the array
testlib.access_array(double_array, size)