why not datetime.strptime() ?

[David M. Cooke]

Joshua Spoerri <josh at yucs.org> writes:

> Skip Montanaro <skip <at> pobox.com> writes:
>> josh> Shouldn't datetime have strptime?
>> If someone wants to get their feet wet with extension module
>> programming
>> this might be a good place to start.  Mostly, I think nobody who has
>> needed/wanted it so far has the round tuits available to spend on the
>> task.
>
> OK, it was pretty straightforward. Thanks for the direction.
>
> To whom should I send the patch (attached)?

Submit it to the patch tracker on sourceforge.

But first, some constructive criticism:

> --- Modules/datetimemodule.c.orig	2003-10-20 10:34:46.000000000 -0400
> +++ Modules/datetimemodule.c	2005-01-10 20:58:38.884823296 -0500
> @@ -3774,6 +3774,32 @@
>  	return result;
>  }
>  
> +/* Return new datetime from time.strptime(). */
> +static PyObject *
> +datetime_strptime(PyObject *cls, PyObject *args)
> +{
> +	PyObject *result = NULL, *obj, *module;
> +	const char *string, *format;
> +
> +	if (!PyArg_ParseTuple(args, "ss:strptime", &string, &format))
> +		return NULL;
> +	if ((module = PyImport_ImportModule("time")) == NULL)
> +		return NULL;
> +	obj = PyObject_CallMethod(module, "strptime", "ss", string, format);
> +	Py_DECREF(module);

You don't check for errors: an exception being thrown by
PyObject_CallMethod will return obj == NULL.

If there's a module in sys.path called time that overrides the stdlib
time, things will fail, and you should be able to catch that.

> +	result = PyObject_CallFunction(cls, "iiiiiii",
> +		PyInt_AsLong(PySequence_GetItem(obj, 0)),
> +		PyInt_AsLong(PySequence_GetItem(obj, 1)),
> +		PyInt_AsLong(PySequence_GetItem(obj, 2)),
> +		PyInt_AsLong(PySequence_GetItem(obj, 3)),
> +		PyInt_AsLong(PySequence_GetItem(obj, 4)),
> +		PyInt_AsLong(PySequence_GetItem(obj, 5)),
> +		PyInt_AsLong(PySequence_GetItem(obj, 6)));

Are you positive those PySequence_GetItem calls will succeed? That
they will return Python integers?

> +	Py_DECREF(obj);
> +	return result;
> +}
> +
>  /* Return new datetime from date/datetime and time arguments. */
>  static PyObject *
>  datetime_combine(PyObject *cls, PyObject *args, PyObject *kw)
> @@ -4385,6 +4411,11 @@
>  	 PyDoc_STR("timestamp -> UTC datetime from a POSIX timestamp "
>  	 	   "(like time.time()).")},
>  
> +	{"strptime", (PyCFunction)datetime_strptime,
> +	 METH_VARARGS | METH_CLASS,
> +	 PyDoc_STR("strptime -> new datetime parsed from a string"
> +	 	   "(like time.strptime()).")},
> +
>  	{"combine", (PyCFunction)datetime_combine,
>  	 METH_VARARGS | METH_KEYWORDS | METH_CLASS,
>  	 PyDoc_STR("date, time -> datetime with same date and time fields")},

It probably would help to add some documentation to add to the
datetime module documentation.

-- 
|>|\/|<
/--------------------------------------------------------------------------\
|David M. Cooke
|cookedm(at)physics(dot)mcmaster(dot)ca