Writing a CPython extension - calling another sibbling method ?

[MRAB]

On 2019-11-18 20:15, R.Wieser wrote:
> MRAB,
> 
>> One possibility is to refactor the code so that py_proc1 and py_proc2 
>> themselves just handle their arguments and then call the function that 
>> does the actual work.
> 
> The thing is that the arguments of py_proc1 and py_proc2 are the same, but
> for a single argument.   Which means that letting both of them first parse
> their own arguments means duplicated code.    Which I do not really want and
> thus try to evade
> 
> But yes, that is a possibility too.  The "the function that does the actual
> work" part is what I tried to describe with my second example.
> 
>> A clunkier way would be to make a new tuple that consists of the prepended 
>> item and the items of args and pass that to py_proc1 as its args.
> 
> That is what I tried to describe with my first example.
> 
> The thing is I have no clue about what the above calling should look like
> (though I think I already found how to append my argument to the "args"
> string-object).
> 
> In other words, do you have any idea of what either of those calling methods
> should look like ?   An example perhaps ?   Having only encountered the
> CPython API two days ago I'm still fumbling in the dark I'm afraid.
> 
It could be something like this:


static PyObject *py_proc2(PyObject *self, PyObject *args)
{
     /*** TODO: Add error checking. ***/
     PyObject* prepend_arg;
     PyObject* prepend_tuple;
     PyObject* new_args;
     PyObject* result;

     /* The object to be prepended. */
     prepend_arg = PyUnicode_FromString("foo");

     /* Make a tuple from the prepended object. */
     prepend_tuple = BuildValue("(O)", prepend_arg);

     /* No longer need prepend_arg. */
     Py_DECREF(prepend_arg);

     /* Make the new argument list. */
     new_args = PySequence_Concat(prepend, args);

     /* No longer need prepend_tuple. */
     Py_DECREF(prepend_tuple);

     /* Call the other method. */
     result = py_proc1(self, new_args);

     /* No longer need new_args. */
     Py_DECREF(new_args);

     return result;
}