File: //usr/share/doc/python-docs-2.4.3/html/ext/buildValue.html
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<html>
<head>
<link rel="STYLESHEET" href="ext.css" type='text/css' />
<link rel="SHORTCUT ICON" href="../icons/pyfav.png" type="image/png" />
<link rel='start' href='../index.html' title='Python Documentation Index' />
<link rel="first" href="ext.html" title='Extending and Embedding the Python Interpreter' />
<link rel='contents' href='contents.html' title="Contents" />
<link rel='last' href='about.html' title='About this document...' />
<link rel='help' href='about.html' title='About this document...' />
<link rel="next" href="refcounts.html" />
<link rel="prev" href="parseTupleAndKeywords.html" />
<link rel="parent" href="intro.html" />
<link rel="next" href="refcounts.html" />
<meta name='aesop' content='information' />
<title>1.9 Building Arbitrary Values
</title>
</head>
<body>
<DIV CLASS="navigation">
<div id='top-navigation-panel' xml:id='top-navigation-panel'>
<table align="center" width="100%" cellpadding="0" cellspacing="2">
<tr>
<td class='online-navigation'><a rel="prev" title="1.8 Keyword Parameters for"
href="parseTupleAndKeywords.html"><img src='../icons/previous.png'
border='0' height='32' alt='Previous Page' width='32' /></A></td>
<td class='online-navigation'><a rel="parent" title="1. Extending Python with"
href="intro.html"><img src='../icons/up.png'
border='0' height='32' alt='Up One Level' width='32' /></A></td>
<td class='online-navigation'><a rel="next" title="1.10 Reference Counts"
href="refcounts.html"><img src='../icons/next.png'
border='0' height='32' alt='Next Page' width='32' /></A></td>
<td align="center" width="100%">Extending and Embedding the Python Interpreter</td>
<td class='online-navigation'><a rel="contents" title="Table of Contents"
href="contents.html"><img src='../icons/contents.png'
border='0' height='32' alt='Contents' width='32' /></A></td>
<td class='online-navigation'><img src='../icons/blank.png'
border='0' height='32' alt='' width='32' /></td>
<td class='online-navigation'><img src='../icons/blank.png'
border='0' height='32' alt='' width='32' /></td>
</tr></table>
<div class='online-navigation'>
<b class="navlabel">Previous:</b>
<a class="sectref" rel="prev" href="parseTupleAndKeywords.html">1.8 Keyword Parameters for</A>
<b class="navlabel">Up:</b>
<a class="sectref" rel="parent" href="intro.html">1. Extending Python with</A>
<b class="navlabel">Next:</b>
<a class="sectref" rel="next" href="refcounts.html">1.10 Reference Counts</A>
</div>
<hr /></div>
</DIV>
<!--End of Navigation Panel-->
<H1><A NAME="SECTION003900000000000000000"></A><A NAME="buildValue"></A>
<BR>
1.9 Building Arbitrary Values
</H1>
<P>
This function is the counterpart to <tt class="cfunction">PyArg_ParseTuple()</tt>. It is
declared as follows:
<P>
<div class="verbatim"><pre>
PyObject *Py_BuildValue(char *format, ...);
</pre></div>
<P>
It recognizes a set of format units similar to the ones recognized by
<tt class="cfunction">PyArg_ParseTuple()</tt>, but the arguments (which are input to the
function, not output) must not be pointers, just values. It returns a
new Python object, suitable for returning from a C function called
from Python.
<P>
One difference with <tt class="cfunction">PyArg_ParseTuple()</tt>: while the latter
requires its first argument to be a tuple (since Python argument lists
are always represented as tuples internally),
<tt class="cfunction">Py_BuildValue()</tt> does not always build a tuple. It builds
a tuple only if its format string contains two or more format units.
If the format string is empty, it returns <code>None</code>; if it contains
exactly one format unit, it returns whatever object is described by
that format unit. To force it to return a tuple of size 0 or one,
parenthesize the format string.
<P>
Examples (to the left the call, to the right the resulting Python value):
<P>
<div class="verbatim"><pre>
Py_BuildValue("") None
Py_BuildValue("i", 123) 123
Py_BuildValue("iii", 123, 456, 789) (123, 456, 789)
Py_BuildValue("s", "hello") 'hello'
Py_BuildValue("ss", "hello", "world") ('hello', 'world')
Py_BuildValue("s#", "hello", 4) 'hell'
Py_BuildValue("()") ()
Py_BuildValue("(i)", 123) (123,)
Py_BuildValue("(ii)", 123, 456) (123, 456)
Py_BuildValue("(i,i)", 123, 456) (123, 456)
Py_BuildValue("[i,i]", 123, 456) [123, 456]
Py_BuildValue("{s:i,s:i}",
"abc", 123, "def", 456) {'abc': 123, 'def': 456}
Py_BuildValue("((ii)(ii)) (ii)",
1, 2, 3, 4, 5, 6) (((1, 2), (3, 4)), (5, 6))
</pre></div>
<P>
<DIV CLASS="navigation">
<div class='online-navigation'>
<p></p><hr />
<table align="center" width="100%" cellpadding="0" cellspacing="2">
<tr>
<td class='online-navigation'><a rel="prev" title="1.8 Keyword Parameters for"
href="parseTupleAndKeywords.html"><img src='../icons/previous.png'
border='0' height='32' alt='Previous Page' width='32' /></A></td>
<td class='online-navigation'><a rel="parent" title="1. Extending Python with"
href="intro.html"><img src='../icons/up.png'
border='0' height='32' alt='Up One Level' width='32' /></A></td>
<td class='online-navigation'><a rel="next" title="1.10 Reference Counts"
href="refcounts.html"><img src='../icons/next.png'
border='0' height='32' alt='Next Page' width='32' /></A></td>
<td align="center" width="100%">Extending and Embedding the Python Interpreter</td>
<td class='online-navigation'><a rel="contents" title="Table of Contents"
href="contents.html"><img src='../icons/contents.png'
border='0' height='32' alt='Contents' width='32' /></A></td>
<td class='online-navigation'><img src='../icons/blank.png'
border='0' height='32' alt='' width='32' /></td>
<td class='online-navigation'><img src='../icons/blank.png'
border='0' height='32' alt='' width='32' /></td>
</tr></table>
<div class='online-navigation'>
<b class="navlabel">Previous:</b>
<a class="sectref" rel="prev" href="parseTupleAndKeywords.html">1.8 Keyword Parameters for</A>
<b class="navlabel">Up:</b>
<a class="sectref" rel="parent" href="intro.html">1. Extending Python with</A>
<b class="navlabel">Next:</b>
<a class="sectref" rel="next" href="refcounts.html">1.10 Reference Counts</A>
</div>
</div>
<hr />
<span class="release-info">Release 2.4.3, documentation updated on 29 March 2006.</span>
</DIV>
<!--End of Navigation Panel-->
<ADDRESS>
See <i><a href="about.html">About this document...</a></i> for information on suggesting changes.
</ADDRESS>
</BODY>
</HTML>