PyArg_Parse vs PyArg_ParseTuple
ignacio at openservices.net
Wed Oct 17 20:20:08 CEST 2001
On Wed, 17 Oct 2001, David Brady wrote:
> >-----Original Message-----
> > From: Ignacio Vazquez-Abrams [mailto:ignacio at openservices.net]
> > Sent: Tuesday, October 16, 2001 7:42 PM
> > > I read in the documentatian that PyArg_Parse() is
> > deprecated, so I would
> > > like to get this working correctly.
> > You're misunderstanding what PyArg_Parse() and
> > PyArg_ParseTuple() are used
> > for. They are used for when a C function is called by a
> > Python program, not
> > the other way around. In your case you should probably be
> > using one of the
> > PyInt_As*() or PyLong_As*() functions.
> Okay, two things. First, thank you for replying! The python list is as
> responsive and useful as the language!
> Second, I'm a little confused by your explanation. The code I posted is
> copied almost straight from Programming Python (2e, p1157,
Huh, interesting. Nuke. Housefly.
> Also, my reading of Programming Python, Python Essential Reference, and
> the online Extending/Embedding Tutorial has led me to believe that
> Py_BuildValue() for moving data from C types to Python types, and
> PyArg_Parse*() are for going the other direction. The only difference
> between embedding and extending is that the order of their use is
> reversed. Extensions in C have to Parse the arguments passed in from
> Python, and have to Build the return value, whereas embedding code has
> to Build the arguments and Parse the return. In both cases, C-to-Python
> is a Build, where Python-to-C is a Parse.
> I may be wrong. But at least this lets you know I'm trying! :-)
Well, you can do it that way, but see my previous comment above. If you know
that the PyObject is actually just a single value, then PyArg_Parse*() is
> Thank you for pointing out PyInt_As* and PyInt_From*. They appear to do
> exactly what I need in this case as well. After reading their
> documentation, I think the difference between 'val = PyInt_AsLong(parg)'
> and 'PyArg_Parse(parg, "d", &val)' is that PyArg_Parse() could handle
> more than one object at a time, where PyInt_AsLong() requires that I
> pass it a single PyObject that contains an integer. Do I understand
> this correctly?
> Finally, this brings me back to my original question. Why does
> PyArg_ParseTuple() not work? I should point out that this is ultimately
> intended for an embedded macro language, so there will have to be some
> extension code involved eventually as well.
It has to do with the "Tuple" part of the function name. PyArg_ParseTuple()
expects to be decoding a tuple, but the function only returns an integer.
Ignacio Vazquez-Abrams <ignacio at openservices.net>
"As far as I can tell / It doesn't matter who you are /
If you can believe there's something worth fighting for."
- "Parade", Garbage
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