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<FONT><h3>Code Examples</h3>
<h5>
Listing 6.1 Benchmark Extension (File benchmarkmodule.c)</h5>
<PRE Class="monofont">
1: #include "<Python.h>"
2:
3: static PyObject *
4: benchmark_generate(PyObject *self, PyObject *args);
5: {
6: int index, number_of_arguments;
7: PyObject *numberslist = NULL;
8: PyObject *check_value = NULL;
9: PyFloatObject *aux_float = NULL;
10: double element_value;
11: double minimum_value = 100;
12: double maximum_value = 0;
13: char *exist_check;
14:
15: if (!PyArg_ParseTuple (args, "OO", &numberslist, &check_value))
16: return NULL;
17:
18: if (!PyList_Check(numberslist))
19: {
20: PyErr_SetString(PyExc_TypeError, "Invalid list of values !");
21: return NULL;
22: }
23:
24: if (!PyFloat_Check(check_value))
25: {
26: PyErr_SetString(PyExc_TypeError, "Invalid checking value !");
27: return NULL;
28: }
29:
30: number_of_arguments = PyList_Size(numberslist);
31: exist_check = "No";
32:
33: for (index=0; index<number_of_arguments; index++)
34: {
35: aux_float = (PyFloatObject *) PyList_GetItem(numberslist, index);
36: if (!PyFloat_Check(aux_float))
37: {
38: PyErr_SetString(PyExc_TypeError, "Invalid list value !");
39: return NULL;
40: }
41: element_value = PyFloat_AsDouble(aux_float);
42: if (element_value < 0 )
43: {
44: PyErr_SetString(PyExc_TypeError, "The values cannot be less than 0
!");
45: return NULL;
46: }
47:
48: if (element_value > 100 )
49: {
50: PyErr_SetString(PyExc_TypeError,
"The values cannot be greater than 100 !");
51: return NULL;
52: }
53:
54: if (element_value < minimum_value)
55: minimum_value = element_value;
56:
57: if (element_value > maximum_value)
58: maximum_value = element_value;
59:
60: if (element_value == PyFloat_AsDouble(check_value))
61: exist_check = "Yes";
62: }
63: return Py_BuildValue("(ffs)", minimum_value, maximum_value,
exist_check );
64: }
65:
66: static PyMethodDef benchmark_methods[] = {
67: {"generate", benchmark_generate, METH_VARARGS, "Minimum Value,
Maximum Value"},
68: {NULL, NULL}
69: };
70:
71: DL_EXPORT(void) initbenchmark()
72: {
73: Py_InitModule("benchmark", benchmark_methods);
74: }
</PRE>
<P>Line 9: <tt clASS="monofont">PyFloatObject</Tt> is a subtype of <tt class="monofont">PyObject.</tt></p>
<p>Line 18: Checks whether the first argument is a list.</p>
<p>Line 24: Checks whether the type of the second argument is a float.</p>
<p>Line 26: Raises a <tt clAss="monofont">TypeError</Tt> exception.</p>
<p>Line 30: Returns the list's length.</P>
<p>Line 60: <tt cLass="monofont">PyFloat_AsDouble</TT> converts a Python Float into a C double.</P>
<P>Next, you can see a small interaction with this program. To execute it, we have to pass two arguments: The first one is a list of numbers, and the second one is a float number. This program returns the minimum and maximum values from the list, along with a logical test that informs whether the float number is part of the list.</p>
<pre>
Python 1.5.2 (#0, May 30 2000, 00:16:14) [MSC 32 bit (Intel)] on win32
Copyright 1991-1995 Stichting Mathematisch Centrum, Amsterdam
>>> import benchmark
>>> benchmark.generate([1.1],1.1)
(1.1, 1.1, 'Yes')
>>> benchmark.generate([1,2,3],4.5)
(1.0, 3.0, 'No')
>>>
</PRE>
<H4>Wrapping C Functions</h4>
<p>By wrapping functions, you can use C code files, without changing them. Every time you feel the need to include a C source code file in your Python project, it is necessary to create a special module that wraps its functions, and to include a reference to the file in the <tt CLASs="monofont">python15.dsp.</tt></p>
<P>The next example wraps the functions stored in the <TT Class="monofont">cfunctions.c</tt> file.</p>
<h5>
Listing 6.2 File: <tt class="monofont">cfunctions.c</tt></h5>
<prE clAss="monofont">
#include <stdio.h>
void display_info(char *user, char *domain, char *country) {
if (country == "USA")
printf("%s@%s\n", user, domain);
else
printf("%s@%s.%s\n", user, domain, country);
}
int calc_year (int f_year, int m_year, int l_year) {
int result;
result = ((l_year + m_year + f_year) / 3);
return result;
}
</pRe>
<h5>
Listing 6.3 File: <tt ClasS="monofont">wrappermodule.c</TT></H5>
<pre cLASS="monofont">
1: #include "Python.h"
2:
3: extern void display_info(char *, char *, char *);
4: extern int calc_year(int, int, int);
5:
6: static PyObject *wrapper_display_info(PyObject *self, PyObject *args,
PyObject *kwargs)
7: {
8: char *user = "None";
9: char *domain = "None";
10: char *country = "None";
11: static char *keywords[] = {"user","domain","country",NULL};
12:
13: if (!PyArg_ParseTupleAndKeywords(args, kwargs, "|sss", keywords,
&user, &domain, &country)){
14: return NULL;
15: }
16:
17: display_info(user, domain, country);
18: return Py_BuildValue("");
19: }
20:
21: static PyObject *wrapper_calc_year(PyObject *self, PyObject *args) {
22: int f_year, m_year, l_year, result;
23: if (!PyArg_ParseTuple(args, "iii", &f_year, &m_year, &l_year)) {
24: return NULL;
25: }
26: result = calc_year(f_year, m_year, l_year);
27: return Py_BuildValue("i", result);
28: }
29:
30: static PyMethodDef wrappermethods[] = {
31: {"display_info", wrapper_display_info, METH_VARARGS|METH_KEYWORDS},
32: {"calc_year", wrapper_calc_year, METH_VARARGS},
33: {NULL, NULL}
34: };
35:
36: void initwrapper() {
37: Py_InitModule("wrapper", wrappermethods);
38: }
</pre>
<p>Lines 3 and 4: Identify which functions are external to this file.</P>
<P>Line 11: Creates a dictionary of keywords to be accepted by the function.</P>
<P>Line 13: <tt clASS="monofont">PyArg_ParseTupleAndKeywords()</Tt> parses the Python-level parameters by accepting a third <tt class="monofont">"PyObject *"</tt> parameter.</p>
<p>Line 31: The <tt class="monofont">METH_VARARGS|METH_KEYWORDS</tT> clause makes it clear that keyword elements are expected.</p>
<p>Next, you can see a small interaction with this program. The first function builds an email address based on the information provided. The other one calculates the average age of a family of three people based on the number of years that are passed to the function.</P>
<pre>
Python 1.5.2 (#0, May 30 2000, 00:56:46) [MSC 32 bit (Intel)] on win32
Copyright 1991-1995 Stichting Mathematisch Centrum, Amsterdam
>>> import wrapper
>>> wrapper.display_info("andre2530","aol.com","br")
andre2530@aol.com.br
>>> wrapper.calc_year(10, 30, 35)
25
>>>
</Pre>
</foNt>
<P><TABLE width="100%" border=0><TR valign="top"><TD><font size=1 color="#C0C0C0"><br></font></TD><TD align=right><font size=1 color="#C0C0C0">Last updated on 1/30/2002<br>Python Developer's Handbook, © 2002 Sams Publishing</font></TD></TR></TABLE></P>
<TABLE border=0 width="100%" cellspacing=0 cellpadding=0><TR><td align=left width="15%" class="headingsubbarbg"><a href="126.html" title="Summary"><font size="1">< BACK</font></a></td><td align=center width="70%" class="headingsubbarbg"><font size="1"><a href="popanote.asp?pubui=oreilly&bookname=0672319942&snode=127" target="_blank" title="Make a public or private annnotation">Make Note</a> | <a href="127.html" title="Use a Safari bookmark to remember this section">Bookmark</a></font></td><td align=right width="15%" class="headingsubbarbg"><a href="129.html" title="7. Objects Interfacing and Distribution"><font size="1">CONTINUE ></font></a></td></TR></TABLE>
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