I'm trying to use ctypes
. I'm interested in manipulating C structs containing arrays. Consider the following my_library.c
#include <stdio.h>
typedef struct {
double first_array[10];
double second_array[10];
} ArrayStruct;
void print_array_struct(ArrayStruct array_struct){
for (int i = 0; i < 10; i++){
printf("%f
",array_struct.first_array[i]);
}
}
and suppose I've compiled it in a shared library my_so_object.so
From Python I can do something like this
import ctypes
from ctypes import *
myLib = CDLL("c/bin/my_so_object.so")
class ArrayStruct(ctypes.Structure):
_fields_ = [('first_array', ctypes.c_int * 10), ('second_array', ctypes.c_int * 10)]
def __repr__(self):
return 'ciaone'
myLib.print_array_struct.restype = None
myLib.print_array_struct.argtype = ArrayStruct
my_array_type = ctypes.c_int * 10
x1 = my_array_type()
x2 = my_array_type()
a = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
x1[0:9] = a[0:9]
a = [11, 12, 13, 14, 15, 16, 17, 18, 19, 20]
x2[0:9] = a[0:9]
print(my_array_type)
>>> <class '__main__.c_int_Array_10'>
print(x1[2])
>>> 3
print(x2[2])
>>> 13
x = ArrayStruct(x1, x2)
print(x.first_array[0:9])
>>> [1, 2, 3, 4, 5, 6, 7, 8, 9]
So far so good: I've created the correct types and everything seems working fine. But then:
myLib.print_array_struct(x)
>>> 0.000000
>>> 0.000000
>>> 0.000000
>>> 0.000000
>>> 0.000000
>>> 0.000000
>>> 0.000000
>>> 0.000000
>>> 0.000000
>>> 0.000000
I'm clearly missing something. The ArrayStruct
type is recognized (otherwise the call myLib.print_array_struct(x)
would throw an error) but not correctly initialized.
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