[Python-Dev] Using argument clinic to replace timemodule.c:parse_time_t_args()

[Larry Hastings]

Yes, I meant in the definition of the convertor class.  You can fix c_default in converter_init.

On Jan 21, 2014 7:19 PM, Nikolaus Rath <Nikolaus at rath.org> wrote:
>
> Larry Hastings <larry at hastings.org> writes:
> > A comment on your approach so far: I'm very much against giving
> > "default" a default value in the constructor.
>
> You mean in the definition of the custom converter class?
>
> > I realize that hack saves you having to say "= NULL" in a lot of
> > places.  But explicit is better than implicit, and we're going to read
> > these signatures a lot more often than we write them, and I want
> > Clinic signatures to be easy to read at first glance.
> [....]
> > All is not lost!  What follows is rough pseudo-C code, hopefully you
> > can take it from here.
> >
> >    typedef struct {
> >       int set;
> >       time_t when;
> >    } clinic_time_t;
> >    #define DEFAULT_CLINIC_TIME_T {0, 0}
> >
> [...]
> >
> >    /*[python input]
> >    class clinic_time_t_converter(CConverter):
> >         type = 'clinic_time_t'
> >         converter = 'parse_clinic_time_t'
> >         c_default = 'DEFAULT_CLINIC_TIME_T'
> >    [python start generated code]*/
> >    /*[python end generated code: checksum=...]*/
> >
> > Now you can use clinic_time_t.  Parameters declared clinic_time_t can
> > be required, or they can be optional; if they're optional give them a
> > default value of None.
>
> That doesn't work. If the default value is declared for the function
> rather than in the converter definition, it overwrites the C default:
>
> /*[clinic input]
> time.gmtime
>
>     seconds: clinic_time_t=None
>     /
> */
>
> gives:
>
> static PyObject *
> time_gmtime(PyModuleDef *module, PyObject *args)
> {
>     PyObject *return_value = NULL;
>     clinic_time_t seconds = Py_None;
>
>     if (!PyArg_ParseTuple(args,
>         "|O&:gmtime",
>         parse_clinic_time_t, &seconds))
>         goto exit;
>     return_value = time_gmtime_impl(module, seconds);
>
> so the default for seconds is now Py_None instead of
> DEFAULT_CLINIC_TIME_T'.
>
> Best,
> Nikolaus
>
> -- 
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