如何在python中使用ctypes初始化和传递自引用结构？

Question

I have the following structure in C:

struct Entry_t{
    char *key; 
    int data_type; 
    int nbitems; 
    size_t offset; 
    int size; 
    Entry_t *pcfg;
};

and the following function in C:(i eventually want to initialize the struct and pass it from python to C)

int get_config(void *ctx, Entry_t* pconfig, void *pdest, char *key);

I have defined the same struct in python as follows:

class Entry_t(Structure): pass
Entry_t._fields_ = [
             ('key', c_char_p),
             ('data_type', c_int),
             ('nbitems', c_int),
             ('offset', c_size_t),
             ('size', c_int),
             ('pcfg', POINTER(Entry_t)),
    ]

testctx = Entry_t() //initialize with empty values

I have created Entry_t instance as follows:

type = Entry_t("e",3,1,5,12,POINTER(testctx))

i get this error when creating an instance,

TypeError: expected LP_Entry instance, got CArgObject

How do i properly initialize my entry_t struct?

Answer 1

type = Entry_t("e",3,1,5,12,POINTER(testctx))

When you pass testctx to your object, use the pointer() function (lowercase) as the uppercase variant is used to describe structs rather than construct objects. Also, it is recommended not to shadow builtin Python functions, so consider renaming your variable from "type" to something else.

t1 = Entry_t("e", 3, 1, 5, 12, pointer(testctx))