Porting guide


PyModule_AddObject() is replaced with a regular HPy_SetAttr_s(). There is no HPyModule_AddObject() because it has an unusual refcount behaviour (stealing a reference but only when it returns 0).


Py_tp_dealloc becomes HPy_tp_destroy. We changed the name a little bit because only “lightweight” destructors are supported. Use tp_finalize if you really need to do things with the context or with the handle of the object.

Py_tp_methods, Py_tp_members and Py_tp_getset

Py_tp_methods, Py_tp_members and Py_tp_getset are no longer needed. Methods, members and getsets are specified “flatly” together with the other slots, using the standard mechanism of HPyDef_{METH,MEMBER,GETSET} and HPyType_Spec.defines.


PyList_New(5)/PyList_SET_ITEM() becomes:

HPyListBuilder builder = HPyListBuilder_New(ctx, 5);
HPyListBuilder_Set(ctx, builder, 0, h_item0);
HPyListBuilder_Append(ctx, builder, h_item5);
HPy h_list = HPyListBuilder_Build(ctx, builder);

For lists of (say) integers:

HPyListBuilder_i builder = HPyListBuilder_i_New(ctx, 5);
HPyListBuilder_i_Set(ctx, builder, 0, 42);
HPy h_list = HPyListBuilder_i_Build(ctx, builder);

And similar for building tuples or bytes

PyObject_Call and PyObject_CallObject

Both PyObject_Call and PyObject_CallObject are replaced by HPy_CallTupleDict(callable, args, kwargs) in which either or both of args and kwargs may be null handles.

PyObject_Call(callable, args, kwargs) becomes:

HPy result = HPy_CallTupleDict(ctx, callable, args, kwargs);

PyObject_CallObject(callable, args) becomes:

HPy result = HPy_CallTupleDict(ctx, callable, args, HPy_NULL);

If args is not a handle to a tuple or kwargs is not a handle to a dictionary, HPy_CallTupleDict will return HPy_NULL and raise a TypeError. This is different to PyObject_Call and PyObject_CallObject which may segfault instead.


The buffer API in HPy is implemented using the HPy_buffer struct, which looks very similar to Py_buffer (refer to the CPython documentation for the meaning of the fields):

typedef struct {
    void *buf;
    HPy obj;
    HPy_ssize_t len;
    HPy_ssize_t itemsize;
    int readonly;
    int ndim;
    char *format;
    HPy_ssize_t *shape;
    HPy_ssize_t *strides;
    HPy_ssize_t *suboffsets;
    void *internal;
} HPy_buffer;

Buffer slots for HPy types are specified using slots HPy_bf_getbuffer and HPy_bf_releasebuffer on all supported Python versions, even though the matching PyType_Spec slots, Py_bf_getbuffer and Py_bf_releasebuffer, are only available starting from CPython 3.9.