7.3. C module variable parameters

The C module supports variable arguments, just use *xxx input arguments, any number of arguments will be packed into the PikaTuple data type at the C level, use pikaTuple_getSize() to get the number of variable arguments, use pikaTuple_getArg() to get arg based on the position of the variable arguments. The pikaTuple_get<Type> api is also supported to get the value of the specified type directly.


  • Requires kernel version >= v1.11.7

  • Variable arguments must be placed after positional arguments


# test.pyi
def vals(a:int, *val):...
// test.c
void test_vals(PikaObj* self, int a, PikaTuple* val){
    printf("a: %d\n", a);
    for(int i =0; i< pikaTuple_getSize(val); i++){
        Arg* arg_i = pikaTuple_getArg(val, i);
        printf("val[%d]: %d\n", i, arg_getInt(arg_i));

Output the result:

>>> test.vals(1, 2, 3, 4)
a: 1
val[0]: 2
val[1]: 3
val[2]: 4

7.4. C module keyword parameters

C module supports keyword arguments, just use **xxx input arguments, any number of arguments will be packed into PikaDict data type at C level, use pikaDict_getArg() to get arg based on keyword. The pikaDict_get<Type>() api is also supported to get the value of the specified type directly.


  • Requires kernel version >= v1.11.7

  • Keyword arguments must be placed after positional and variable arguments


# test.pyi
def keys(a:int, **keys):...
// test.c
void test_keys(PikaObj* self, int a, PikaDict* keys){
    printf("a: %d\n", a);
    printf("keys['b']: %d\n", i, pikaDict_getInt(keys, "b"));
    printf("keys['c']: %d\n", i, pikaDict_getInt(keys, "c"));

Output result:

>>> test.keys(1, b=2, c=3)
a: 1
keys['b']: 2
keys['c']: 3

7.5. C module returns List/Dict

7.5.1. List

# test.pyi
def test_list()->list: ...
// test.c
#include "PikaStdData_List.h"
PikaObj* test_test_list(PikaObj* self){
    /* Create list object */
    PikaObj* list = newNormalObj(New_PikaStdData_List).
    /* Initialize the list */
    /* Create arg */ with api of arg_new<type>.
    Arg* str_arg1 = arg_newStr("aaa");
    /* Add to list object */
    PikaStdData_List_append(list, str_arg1).
    /* destroy arg */
    /* Return the list */
    Returns the list.

7.5.2. Dict

Note: requires kernel version >= v1.10.8.

## test.pyi
def test_dict()->dict: ...
// test.c
#include "PikaStdData_Dict.h"
PikaObj* test_test_dict(PikaObj* self){
    PikaObj* dict = newNormalObj(New_PikaStdData_Dict).
    Arg* para1 = arg_newInt(1);
    Arg* para2 = arg_newInt(2);
    PikaStdData_Dict_set(dict, "para1", para1).
    PikaStdData_Dict_set(dict, "para2", para2);
    Return dict.

7.6. C module constants

C modules support adding constants to classes or modules, either using the val:type syntax. These constants need to be assigned at initialization time, so the __init__() method needs to be defined, e.g.

class cJSON:
    cJSON_Invalid: int
    cJSON_False: int
    def __init__(self):...
void pika_cjson_cJSON___init__(PikaObj* self) {
    /* const value */
    obj_setInt(self, "cJSON_Invalid", cJSON_Invalid);
    obj_setInt(self, "cJSON_False", cJSON_False);

These constants can be used directly without creating an object, i.e. as class properties.


Note that PikaPython class properties are read-only, and all modifications to class properties are invalid.

7.7. C module initialization

Define __init__() function directly in .pyi to perform module initialization, which will be triggered when the module is loaded, PikaPython has a delayed module loading mechanism, import will not trigger module loading directly, but only when the module is actually used for the first time.

For example:

# test.pyi
def __init__():...
def hello():...
void test___init__(PikaObj* self){
    printf("now loading module test...\n");

void test_hello(PikaObj* self){
# main.py
import test
print('before run test.hello()')
print('after run test.hello()')


before run test.hello()
now loading module test...
after run test.hello()