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<H1><A NAME="SECTION003800000000000000000"></A><A NAME="parseTupleAndKeywords"></A><a id='l2h-3' xml:id='l2h-3'></a>
<BR>
1.8 Keyword Parameters for Extension Functions

</H1>

<P>
<a id='l2h-4' xml:id='l2h-4'></a>

<P>
The <tt class="cfunction">PyArg_ParseTupleAndKeywords()</tt> function is declared as
follows:

<P>
<div class="verbatim"><pre>
int PyArg_ParseTupleAndKeywords(PyObject *arg, PyObject *kwdict,
                                char *format, char *kwlist[], ...);
</pre></div>

<P>
The <var>arg</var> and <var>format</var> parameters are identical to those of the
<tt class="cfunction">PyArg_ParseTuple()</tt> function.  The <var>kwdict</var> parameter
is the dictionary of keywords received as the third parameter from the
Python runtime.  The <var>kwlist</var> parameter is a <tt class="constant">NULL</tt>-terminated
list of strings which identify the parameters; the names are matched
with the type information from <var>format</var> from left to right.  On
success, <tt class="cfunction">PyArg_ParseTupleAndKeywords()</tt> returns true,
otherwise it returns false and raises an appropriate exception.

<P>
<span class="note"><b class="label">Note:</b>
Nested tuples cannot be parsed when using keyword
arguments!  Keyword parameters passed in which are not present in the
<var>kwlist</var> will cause <tt class="exception">TypeError</tt> to be raised.</span>

<P>
Here is an example module which uses keywords, based on an example by
Geoff Philbrick (<span class="email">philbrick@hks.com</span>):
<P>
<div class="verbatim"><pre>
#include "Python.h"

static PyObject *
keywdarg_parrot(PyObject *self, PyObject *args, PyObject *keywds)
{
    int voltage;
    char *state = "a stiff";
    char *action = "voom";
    char *type = "Norwegian Blue";

    static char *kwlist[] = {"voltage", "state", "action", "type", NULL};

    if (!PyArg_ParseTupleAndKeywords(args, keywds, "i|sss", kwlist,
                                     &amp;voltage, &amp;state, &amp;action, &amp;type))
        return NULL;

    printf("-- This parrot wouldn't %s if you put %i Volts through it.\n",
           action, voltage);
    printf("-- Lovely plumage, the %s -- It's %s!\n", type, state);

    Py_INCREF(Py_None);

    return Py_None;
}

static PyMethodDef keywdarg_methods[] = {
    /* The cast of the function is necessary since PyCFunction values
     * only take two PyObject* parameters, and keywdarg_parrot() takes
     * three.
     */
    {"parrot", (PyCFunction)keywdarg_parrot, METH_VARARGS | METH_KEYWORDS,
     "Print a lovely skit to standard output."},
    {NULL, NULL, 0, NULL}   /* sentinel */
};
</pre></div>

<P>
<div class="verbatim"><pre>
void
initkeywdarg(void)
{
  /* Create the module and add the functions */
  Py_InitModule("keywdarg", keywdarg_methods);
}
</pre></div>

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<span class="release-info">Release 2.4.2, documentation updated on 28 September 2005.</span>
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