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<li><a class="reference internal" href="#">Parsing arguments and building values</a><ul>
<li><a class="reference internal" href="#parsing-arguments">Parsing arguments</a><ul>
<li><a class="reference internal" href="#strings-and-buffers">Strings and buffers</a></li>
<li><a class="reference internal" href="#numbers">Numbers</a></li>
<li><a class="reference internal" href="#other-objects">Other objects</a></li>
<li><a class="reference internal" href="#api-functions">API Functions</a></li>
</ul>
</li>
<li><a class="reference internal" href="#building-values">Building values</a></li>
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 <section id="parsing-arguments-and-building-values">
<h1>Parsing arguments and building values<a class="headerlink" href="#parsing-arguments-and-building-values" title="Permalink to this headline">¶</a></h1>
These functions are useful when creating your own extensions functions and
methods. Additional information and examples are available in
<a class="reference internal" href="../extending/index.html#extending-index">Extending and Embedding the Python Interpreter</a>.
The first three of these functions described, <a class="reference internal" href="#c.PyArg_ParseTuple" title="PyArg_ParseTuple"><code class="xref c c-func docutils literal notranslate">PyArg_ParseTuple()</code></a>,
<a class="reference internal" href="#c.PyArg_ParseTupleAndKeywords" title="PyArg_ParseTupleAndKeywords"><code class="xref c c-func docutils literal notranslate">PyArg_ParseTupleAndKeywords()</code></a>, and <a class="reference internal" href="#c.PyArg_Parse" title="PyArg_Parse"><code class="xref c c-func docutils literal notranslate">PyArg_Parse()</code></a>, all use format
strings which are used to tell the function about the expected arguments. The
format strings use the same syntax for each of these functions.
<section id="parsing-arguments">
<h2>Parsing arguments<a class="headerlink" href="#parsing-arguments" title="Permalink to this headline">¶</a></h2>
A format string consists of zero or more “format units.” A format unit
describes one Python object; it is usually a single character or a parenthesized
sequence of format units. With a few exceptions, a format unit that is not a
parenthesized sequence normally corresponds to a single address argument to
these functions. In the following description, the quoted form is the format
unit; the entry in (round) parentheses is the Python object type that matches
the format unit; and the entry in [square] brackets is the type of the C
variable(s) whose address should be passed.
<section id="strings-and-buffers">
<h3>Strings and buffers<a class="headerlink" href="#strings-and-buffers" title="Permalink to this headline">¶</a></h3>
These formats allow accessing an object as a contiguous chunk of memory.
You don’t have to provide raw storage for the returned unicode or bytes
area.
Unless otherwise stated, buffers are not NUL-terminated.
There are three ways strings and buffers can be converted to C:
<ul>
<li>Formats such as <code class="docutils literal notranslate">y*</code> and <code class="docutils literal notranslate">s*</code> fill a <a class="reference internal" href="buffer.html#c.Py_buffer" title="Py_buffer"><code class="xref c c-type docutils literal notranslate">Py_buffer</code></a> structure.
This locks the underlying buffer so that the caller can subsequently use
the buffer even inside a <a class="reference internal" href="init.html#c.Py_BEGIN_ALLOW_THREADS" title="Py_BEGIN_ALLOW_THREADS"><code class="xref c c-type docutils literal notranslate">Py_BEGIN_ALLOW_THREADS</code></a>
block without the risk of mutable data being resized or destroyed.
As a result, you have to call <a class="reference internal" href="buffer.html#c.PyBuffer_Release" title="PyBuffer_Release"><code class="xref c c-func docutils literal notranslate">PyBuffer_Release()</code></a> after you have
finished processing the data (or in any early abort case).</li>
<li>The <code class="docutils literal notranslate">es</code>, <code class="docutils literal notranslate">es#</code>, <code class="docutils literal notranslate">et</code> and <code class="docutils literal notranslate">et#</code> formats allocate the result buffer.
You have to call <a class="reference internal" href="memory.html#c.PyMem_Free" title="PyMem_Free"><code class="xref c c-func docutils literal notranslate">PyMem_Free()</code></a> after you have finished
processing the data (or in any early abort case).</li>
<li>Other formats take a <a class="reference internal" href="../library/stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a> or a read-only <a class="reference internal" href="../glossary.html#term-bytes-like-object">bytes-like object</a>,
such as <a class="reference internal" href="../library/stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate">bytes</code></a>, and provide a <code class="docutils literal notranslate">const char *</code> pointer to
its buffer.
In this case the buffer is “borrowed”: it is managed by the corresponding
Python object, and shares the lifetime of this object.
You won’t have to release any memory yourself.
To ensure that the underlying buffer may be safely borrowed, the object’s
<a class="reference internal" href="typeobj.html#c.PyBufferProcs.bf_releasebuffer" title="PyBufferProcs.bf_releasebuffer"><code class="xref c c-member docutils literal notranslate">PyBufferProcs.bf_releasebuffer</code></a> field must be <code class="docutils literal notranslate">NULL</code>.
This disallows common mutable objects such as <a class="reference internal" href="../library/stdtypes.html#bytearray" title="bytearray"><code class="xref py py-class docutils literal notranslate">bytearray</code></a>,
but also some read-only objects such as <a class="reference internal" href="../library/stdtypes.html#memoryview" title="memoryview"><code class="xref py py-class docutils literal notranslate">memoryview</code></a> of
<a class="reference internal" href="../library/stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate">bytes</code></a>.
Besides this <code class="docutils literal notranslate">bf_releasebuffer</code> requirement, there is no check to verify
whether the input object is immutable (e.g. whether it would honor a request
for a writable buffer, or whether another thread can mutate the data).
</li>
</ul>
<div class="admonition note">
Note
For all <code class="docutils literal notranslate">#</code> variants of formats (<code class="docutils literal notranslate">s#</code>, <code class="docutils literal notranslate">y#</code>, etc.), the macro
<code class="xref c c-macro docutils literal notranslate">PY_SSIZE_T_CLEAN</code> must be defined before including
<code class="file docutils literal notranslate">Python.h</code>. On Python 3.9 and older, the type of the length argument
is <a class="reference internal" href="intro.html#c.Py_ssize_t" title="Py_ssize_t"><code class="xref c c-type docutils literal notranslate">Py_ssize_t</code></a> if the <code class="xref c c-macro docutils literal notranslate">PY_SSIZE_T_CLEAN</code> macro is defined,
or int otherwise.
</div>
<dl>
<dt><code class="docutils literal notranslate">s</code> (<a class="reference internal" href="../library/stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a>) [const char *]</dt><dd>Convert a Unicode object to a C pointer to a character string.
A pointer to an existing string is stored in the character pointer
variable whose address you pass. The C string is NUL-terminated.
The Python string must not contain embedded null code points; if it does,
a <a class="reference internal" href="../library/exceptions.html#ValueError" title="ValueError"><code class="xref py py-exc docutils literal notranslate">ValueError</code></a> exception is raised. Unicode objects are converted
to C strings using <code class="docutils literal notranslate">'utf-8'</code> encoding. If this conversion fails, a
<a class="reference internal" href="../library/exceptions.html#UnicodeError" title="UnicodeError"><code class="xref py py-exc docutils literal notranslate">UnicodeError</code></a> is raised.
<div class="admonition note">
Note
This format does not accept <a class="reference internal" href="../glossary.html#term-bytes-like-object">bytes-like objects</a>. If you want to accept
filesystem paths and convert them to C character strings, it is
preferable to use the <code class="docutils literal notranslate">O&amp;</code> format with <a class="reference internal" href="unicode.html#c.PyUnicode_FSConverter" title="PyUnicode_FSConverter"><code class="xref c c-func docutils literal notranslate">PyUnicode_FSConverter()</code></a>
as converter.
</div>
<div class="versionchanged">
Changed in version 3.5: Previously, <a class="reference internal" href="../library/exceptions.html#TypeError" title="TypeError"><code class="xref py py-exc docutils literal notranslate">TypeError</code></a> was raised when embedded null code points
were encountered in the Python string.
</div>
</dd>
<dt><code class="docutils literal notranslate">s*</code> (<a class="reference internal" href="../library/stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a> or <a class="reference internal" href="../glossary.html#term-bytes-like-object">bytes-like object</a>) [Py_buffer]</dt><dd>This format accepts Unicode objects as well as bytes-like objects.
It fills a <a class="reference internal" href="buffer.html#c.Py_buffer" title="Py_buffer"><code class="xref c c-type docutils literal notranslate">Py_buffer</code></a> structure provided by the caller.
In this case the resulting C string may contain embedded NUL bytes.
Unicode objects are converted to C strings using <code class="docutils literal notranslate">'utf-8'</code> encoding.
</dd>
<dt><code class="docutils literal notranslate">s#</code> (<a class="reference internal" href="../library/stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a>, read-only <a class="reference internal" href="../glossary.html#term-bytes-like-object">bytes-like object</a>) [const char *, <a class="reference internal" href="intro.html#c.Py_ssize_t" title="Py_ssize_t"><code class="xref c c-type docutils literal notranslate">Py_ssize_t</code></a>]</dt><dd>Like <code class="docutils literal notranslate">s*</code>, except that it provides a <a class="reference internal" href="#c-arg-borrowed-buffer">borrowed buffer</a>.
The result is stored into two C variables,
the first one a pointer to a C string, the second one its length.
The string may contain embedded null bytes. Unicode objects are converted
to C strings using <code class="docutils literal notranslate">'utf-8'</code> encoding.
</dd>
<dt><code class="docutils literal notranslate">z</code> (<a class="reference internal" href="../library/stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a> or <code class="docutils literal notranslate">None</code>) [const char *]</dt><dd>Like <code class="docutils literal notranslate">s</code>, but the Python object may also be <code class="docutils literal notranslate">None</code>, in which case the C
pointer is set to <code class="docutils literal notranslate">NULL</code>.
</dd>
<dt><code class="docutils literal notranslate">z*</code> (<a class="reference internal" href="../library/stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a>, <a class="reference internal" href="../glossary.html#term-bytes-like-object">bytes-like object</a> or <code class="docutils literal notranslate">None</code>) [Py_buffer]</dt><dd>Like <code class="docutils literal notranslate">s*</code>, but the Python object may also be <code class="docutils literal notranslate">None</code>, in which case the
<code class="docutils literal notranslate">buf</code> member of the <a class="reference internal" href="buffer.html#c.Py_buffer" title="Py_buffer"><code class="xref c c-type docutils literal notranslate">Py_buffer</code></a> structure is set to <code class="docutils literal notranslate">NULL</code>.
</dd>
<dt><code class="docutils literal notranslate">z#</code> (<a class="reference internal" href="../library/stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a>, read-only <a class="reference internal" href="../glossary.html#term-bytes-like-object">bytes-like object</a> or <code class="docutils literal notranslate">None</code>) [const char *, <a class="reference internal" href="intro.html#c.Py_ssize_t" title="Py_ssize_t"><code class="xref c c-type docutils literal notranslate">Py_ssize_t</code></a>]</dt><dd>Like <code class="docutils literal notranslate">s#</code>, but the Python object may also be <code class="docutils literal notranslate">None</code>, in which case the C
pointer is set to <code class="docutils literal notranslate">NULL</code>.
</dd>
<dt><code class="docutils literal notranslate">y</code> (read-only <a class="reference internal" href="../glossary.html#term-bytes-like-object">bytes-like object</a>) [const char *]</dt><dd>This format converts a bytes-like object to a C pointer to a
<a class="reference internal" href="#c-arg-borrowed-buffer">borrowed</a> character string;
it does not accept Unicode objects. The bytes buffer must not
contain embedded null bytes; if it does, a <a class="reference internal" href="../library/exceptions.html#ValueError" title="ValueError"><code class="xref py py-exc docutils literal notranslate">ValueError</code></a>
exception is raised.
<div class="versionchanged">
Changed in version 3.5: Previously, <a class="reference internal" href="../library/exceptions.html#TypeError" title="TypeError"><code class="xref py py-exc docutils literal notranslate">TypeError</code></a> was raised when embedded null bytes were
encountered in the bytes buffer.
</div>
</dd>
<dt><code class="docutils literal notranslate">y*</code> (<a class="reference internal" href="../glossary.html#term-bytes-like-object">bytes-like object</a>) [Py_buffer]</dt><dd>This variant on <code class="docutils literal notranslate">s*</code> doesn’t accept Unicode objects, only
bytes-like objects. This is the recommended way to accept
binary data.
</dd>
<dt><code class="docutils literal notranslate">y#</code> (read-only <a class="reference internal" href="../glossary.html#term-bytes-like-object">bytes-like object</a>) [const char *, <a class="reference internal" href="intro.html#c.Py_ssize_t" title="Py_ssize_t"><code class="xref c c-type docutils literal notranslate">Py_ssize_t</code></a>]</dt><dd>This variant on <code class="docutils literal notranslate">s#</code> doesn’t accept Unicode objects, only bytes-like
objects.
</dd>
<dt><code class="docutils literal notranslate">S</code> (<a class="reference internal" href="../library/stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate">bytes</code></a>) [PyBytesObject *]</dt><dd>Requires that the Python object is a <a class="reference internal" href="../library/stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate">bytes</code></a> object, without
attempting any conversion. Raises <a class="reference internal" href="../library/exceptions.html#TypeError" title="TypeError"><code class="xref py py-exc docutils literal notranslate">TypeError</code></a> if the object is not
a bytes object. The C variable may also be declared as <a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a>*.
</dd>
<dt><code class="docutils literal notranslate">Y</code> (<a class="reference internal" href="../library/stdtypes.html#bytearray" title="bytearray"><code class="xref py py-class docutils literal notranslate">bytearray</code></a>) [PyByteArrayObject *]</dt><dd>Requires that the Python object is a <a class="reference internal" href="../library/stdtypes.html#bytearray" title="bytearray"><code class="xref py py-class docutils literal notranslate">bytearray</code></a> object, without
attempting any conversion. Raises <a class="reference internal" href="../library/exceptions.html#TypeError" title="TypeError"><code class="xref py py-exc docutils literal notranslate">TypeError</code></a> if the object is not
a <a class="reference internal" href="../library/stdtypes.html#bytearray" title="bytearray"><code class="xref py py-class docutils literal notranslate">bytearray</code></a> object. The C variable may also be declared as <a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a>*.
</dd>
<dt><code class="docutils literal notranslate">u</code> (<a class="reference internal" href="../library/stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a>) [const Py_UNICODE *]</dt><dd>Convert a Python Unicode object to a C pointer to a NUL-terminated buffer of
Unicode characters. You must pass the address of a <a class="reference internal" href="unicode.html#c.Py_UNICODE" title="Py_UNICODE"><code class="xref c c-type docutils literal notranslate">Py_UNICODE</code></a>
pointer variable, which will be filled with the pointer to an existing
Unicode buffer. Please note that the width of a <a class="reference internal" href="unicode.html#c.Py_UNICODE" title="Py_UNICODE"><code class="xref c c-type docutils literal notranslate">Py_UNICODE</code></a>
character depends on compilation options (it is either 16 or 32 bits).
The Python string must not contain embedded null code points; if it does,
a <a class="reference internal" href="../library/exceptions.html#ValueError" title="ValueError"><code class="xref py py-exc docutils literal notranslate">ValueError</code></a> exception is raised.
<div class="versionchanged">
Changed in version 3.5: Previously, <a class="reference internal" href="../library/exceptions.html#TypeError" title="TypeError"><code class="xref py py-exc docutils literal notranslate">TypeError</code></a> was raised when embedded null code points
were encountered in the Python string.
</div>
<div class="deprecated-removed">
Deprecated since version 3.3, will be removed in version 3.12: Part of the old-style <a class="reference internal" href="unicode.html#c.Py_UNICODE" title="Py_UNICODE"><code class="xref c c-type docutils literal notranslate">Py_UNICODE</code></a> API; please migrate to using
<a class="reference internal" href="unicode.html#c.PyUnicode_AsWideCharString" title="PyUnicode_AsWideCharString"><code class="xref c c-func docutils literal notranslate">PyUnicode_AsWideCharString()</code></a>.
</div>
</dd>
<dt><code class="docutils literal notranslate">u#</code> (<a class="reference internal" href="../library/stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a>) [const Py_UNICODE *, <a class="reference internal" href="intro.html#c.Py_ssize_t" title="Py_ssize_t"><code class="xref c c-type docutils literal notranslate">Py_ssize_t</code></a>]</dt><dd>This variant on <code class="docutils literal notranslate">u</code> stores into two C variables, the first one a pointer to a
Unicode data buffer, the second one its length. This variant allows
null code points.
<div class="deprecated-removed">
Deprecated since version 3.3, will be removed in version 3.12: Part of the old-style <a class="reference internal" href="unicode.html#c.Py_UNICODE" title="Py_UNICODE"><code class="xref c c-type docutils literal notranslate">Py_UNICODE</code></a> API; please migrate to using
<a class="reference internal" href="unicode.html#c.PyUnicode_AsWideCharString" title="PyUnicode_AsWideCharString"><code class="xref c c-func docutils literal notranslate">PyUnicode_AsWideCharString()</code></a>.
</div>
</dd>
<dt><code class="docutils literal notranslate">Z</code> (<a class="reference internal" href="../library/stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a> or <code class="docutils literal notranslate">None</code>) [const Py_UNICODE *]</dt><dd>Like <code class="docutils literal notranslate">u</code>, but the Python object may also be <code class="docutils literal notranslate">None</code>, in which case the
<a class="reference internal" href="unicode.html#c.Py_UNICODE" title="Py_UNICODE"><code class="xref c c-type docutils literal notranslate">Py_UNICODE</code></a> pointer is set to <code class="docutils literal notranslate">NULL</code>.
<div class="deprecated-removed">
Deprecated since version 3.3, will be removed in version 3.12: Part of the old-style <a class="reference internal" href="unicode.html#c.Py_UNICODE" title="Py_UNICODE"><code class="xref c c-type docutils literal notranslate">Py_UNICODE</code></a> API; please migrate to using
<a class="reference internal" href="unicode.html#c.PyUnicode_AsWideCharString" title="PyUnicode_AsWideCharString"><code class="xref c c-func docutils literal notranslate">PyUnicode_AsWideCharString()</code></a>.
</div>
</dd>
<dt><code class="docutils literal notranslate">Z#</code> (<a class="reference internal" href="../library/stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a> or <code class="docutils literal notranslate">None</code>) [const Py_UNICODE *, <a class="reference internal" href="intro.html#c.Py_ssize_t" title="Py_ssize_t"><code class="xref c c-type docutils literal notranslate">Py_ssize_t</code></a>]</dt><dd>Like <code class="docutils literal notranslate">u#</code>, but the Python object may also be <code class="docutils literal notranslate">None</code>, in which case the
<a class="reference internal" href="unicode.html#c.Py_UNICODE" title="Py_UNICODE"><code class="xref c c-type docutils literal notranslate">Py_UNICODE</code></a> pointer is set to <code class="docutils literal notranslate">NULL</code>.
<div class="deprecated-removed">
Deprecated since version 3.3, will be removed in version 3.12: Part of the old-style <a class="reference internal" href="unicode.html#c.Py_UNICODE" title="Py_UNICODE"><code class="xref c c-type docutils literal notranslate">Py_UNICODE</code></a> API; please migrate to using
<a class="reference internal" href="unicode.html#c.PyUnicode_AsWideCharString" title="PyUnicode_AsWideCharString"><code class="xref c c-func docutils literal notranslate">PyUnicode_AsWideCharString()</code></a>.
</div>
</dd>
<dt><code class="docutils literal notranslate">U</code> (<a class="reference internal" href="../library/stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a>) [PyObject *]</dt><dd>Requires that the Python object is a Unicode object, without attempting
any conversion. Raises <a class="reference internal" href="../library/exceptions.html#TypeError" title="TypeError"><code class="xref py py-exc docutils literal notranslate">TypeError</code></a> if the object is not a Unicode
object. The C variable may also be declared as <a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a>*.
</dd>
<dt><code class="docutils literal notranslate">w*</code> (read-write <a class="reference internal" href="../glossary.html#term-bytes-like-object">bytes-like object</a>) [Py_buffer]</dt><dd>This format accepts any object which implements the read-write buffer
interface. It fills a <a class="reference internal" href="buffer.html#c.Py_buffer" title="Py_buffer"><code class="xref c c-type docutils literal notranslate">Py_buffer</code></a> structure provided by the caller.
The buffer may contain embedded null bytes. The caller have to call
<a class="reference internal" href="buffer.html#c.PyBuffer_Release" title="PyBuffer_Release"><code class="xref c c-func docutils literal notranslate">PyBuffer_Release()</code></a> when it is done with the buffer.
</dd>
<dt><code class="docutils literal notranslate">es</code> (<a class="reference internal" href="../library/stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a>) [const char *encoding, char **buffer]</dt><dd>This variant on <code class="docutils literal notranslate">s</code> is used for encoding Unicode into a character buffer.
It only works for encoded data without embedded NUL bytes.
This format requires two arguments. The first is only used as input, and
must be a const char* which points to the name of an encoding as a
NUL-terminated string, or <code class="docutils literal notranslate">NULL</code>, in which case <code class="docutils literal notranslate">'utf-8'</code> encoding is used.
An exception is raised if the named encoding is not known to Python. The
second argument must be a char**; the value of the pointer it
references will be set to a buffer with the contents of the argument text.
The text will be encoded in the encoding specified by the first argument.
<a class="reference internal" href="#c.PyArg_ParseTuple" title="PyArg_ParseTuple"><code class="xref c c-func docutils literal notranslate">PyArg_ParseTuple()</code></a> will allocate a buffer of the needed size, copy the
encoded data into this buffer and adjust *buffer to reference the newly
allocated storage. The caller is responsible for calling <a class="reference internal" href="memory.html#c.PyMem_Free" title="PyMem_Free"><code class="xref c c-func docutils literal notranslate">PyMem_Free()</code></a> to
free the allocated buffer after use.
</dd>
<dt><code class="docutils literal notranslate">et</code> (<a class="reference internal" href="../library/stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a>, <a class="reference internal" href="../library/stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate">bytes</code></a> or <a class="reference internal" href="../library/stdtypes.html#bytearray" title="bytearray"><code class="xref py py-class docutils literal notranslate">bytearray</code></a>) [const char *encoding, char **buffer]</dt><dd>Same as <code class="docutils literal notranslate">es</code> except that byte string objects are passed through without
recoding them. Instead, the implementation assumes that the byte string object uses
the encoding passed in as parameter.
</dd>
<dt><code class="docutils literal notranslate">es#</code> (<a class="reference internal" href="../library/stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a>) [const char *encoding, char **buffer, <a class="reference internal" href="intro.html#c.Py_ssize_t" title="Py_ssize_t"><code class="xref c c-type docutils literal notranslate">Py_ssize_t</code></a> *buffer_length]</dt><dd>This variant on <code class="docutils literal notranslate">s#</code> is used for encoding Unicode into a character buffer.
Unlike the <code class="docutils literal notranslate">es</code> format, this variant allows input data which contains NUL
characters.
It requires three arguments. The first is only used as input, and must be a
const char* which points to the name of an encoding as a
NUL-terminated string, or <code class="docutils literal notranslate">NULL</code>, in which case <code class="docutils literal notranslate">'utf-8'</code> encoding is used.
An exception is raised if the named encoding is not known to Python. The
second argument must be a char**; the value of the pointer it
references will be set to a buffer with the contents of the argument text.
The text will be encoded in the encoding specified by the first argument.
The third argument must be a pointer to an integer; the referenced integer
will be set to the number of bytes in the output buffer.
There are two modes of operation:
If *buffer points a <code class="docutils literal notranslate">NULL</code> pointer, the function will allocate a buffer of
the needed size, copy the encoded data into this buffer and set *buffer to
reference the newly allocated storage. The caller is responsible for calling
<a class="reference internal" href="memory.html#c.PyMem_Free" title="PyMem_Free"><code class="xref c c-func docutils literal notranslate">PyMem_Free()</code></a> to free the allocated buffer after usage.
If *buffer points to a non-<code class="docutils literal notranslate">NULL</code> pointer (an already allocated buffer),
<a class="reference internal" href="#c.PyArg_ParseTuple" title="PyArg_ParseTuple"><code class="xref c c-func docutils literal notranslate">PyArg_ParseTuple()</code></a> will use this location as the buffer and interpret the
initial value of *buffer_length as the buffer size. It will then copy the
encoded data into the buffer and NUL-terminate it. If the buffer is not large
enough, a <a class="reference internal" href="../library/exceptions.html#ValueError" title="ValueError"><code class="xref py py-exc docutils literal notranslate">ValueError</code></a> will be set.
In both cases, *buffer_length is set to the length of the encoded data
without the trailing NUL byte.
</dd>
<dt><code class="docutils literal notranslate">et#</code> (<a class="reference internal" href="../library/stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a>, <a class="reference internal" href="../library/stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate">bytes</code></a> or <a class="reference internal" href="../library/stdtypes.html#bytearray" title="bytearray"><code class="xref py py-class docutils literal notranslate">bytearray</code></a>) [const char *encoding, char **buffer, <a class="reference internal" href="intro.html#c.Py_ssize_t" title="Py_ssize_t"><code class="xref c c-type docutils literal notranslate">Py_ssize_t</code></a> *buffer_length]</dt><dd>Same as <code class="docutils literal notranslate">es#</code> except that byte string objects are passed through without recoding
them. Instead, the implementation assumes that the byte string object uses the
encoding passed in as parameter.
</dd>
</dl>
</section>
<section id="numbers">
<h3>Numbers<a class="headerlink" href="#numbers" title="Permalink to this headline">¶</a></h3>
<dl>
<dt><code class="docutils literal notranslate">b</code> (<a class="reference internal" href="../library/functions.html#int" title="int"><code class="xref py py-class docutils literal notranslate">int</code></a>) [unsigned char]</dt><dd>Convert a nonnegative Python integer to an unsigned tiny int, stored in a C
unsigned char.
</dd>
<dt><code class="docutils literal notranslate">B</code> (<a class="reference internal" href="../library/functions.html#int" title="int"><code class="xref py py-class docutils literal notranslate">int</code></a>) [unsigned char]</dt><dd>Convert a Python integer to a tiny int without overflow checking, stored in a C
unsigned char.
</dd>
<dt><code class="docutils literal notranslate">h</code> (<a class="reference internal" href="../library/functions.html#int" title="int"><code class="xref py py-class docutils literal notranslate">int</code></a>) [short int]</dt><dd>Convert a Python integer to a C short int.
</dd>
<dt><code class="docutils literal notranslate">H</code> (<a class="reference internal" href="../library/functions.html#int" title="int"><code class="xref py py-class docutils literal notranslate">int</code></a>) [unsigned short int]</dt><dd>Convert a Python integer to a C unsigned short int, without overflow
checking.
</dd>
<dt><code class="docutils literal notranslate">i</code> (<a class="reference internal" href="../library/functions.html#int" title="int"><code class="xref py py-class docutils literal notranslate">int</code></a>) [int]</dt><dd>Convert a Python integer to a plain C int.
</dd>
<dt><code class="docutils literal notranslate">I</code> (<a class="reference internal" href="../library/functions.html#int" title="int"><code class="xref py py-class docutils literal notranslate">int</code></a>) [unsigned int]</dt><dd>Convert a Python integer to a C unsigned int, without overflow
checking.
</dd>
<dt><code class="docutils literal notranslate">l</code> (<a class="reference internal" href="../library/functions.html#int" title="int"><code class="xref py py-class docutils literal notranslate">int</code></a>) [long int]</dt><dd>Convert a Python integer to a C long int.
</dd>
<dt><code class="docutils literal notranslate">k</code> (<a class="reference internal" href="../library/functions.html#int" title="int"><code class="xref py py-class docutils literal notranslate">int</code></a>) [unsigned long]</dt><dd>Convert a Python integer to a C unsigned long without
overflow checking.
</dd>
<dt><code class="docutils literal notranslate">L</code> (<a class="reference internal" href="../library/functions.html#int" title="int"><code class="xref py py-class docutils literal notranslate">int</code></a>) [long long]</dt><dd>Convert a Python integer to a C long long.
</dd>
<dt><code class="docutils literal notranslate">K</code> (<a class="reference internal" href="../library/functions.html#int" title="int"><code class="xref py py-class docutils literal notranslate">int</code></a>) [unsigned long long]</dt><dd>Convert a Python integer to a C unsigned long long
without overflow checking.
</dd>
<dt><code class="docutils literal notranslate">n</code> (<a class="reference internal" href="../library/functions.html#int" title="int"><code class="xref py py-class docutils literal notranslate">int</code></a>) [<a class="reference internal" href="intro.html#c.Py_ssize_t" title="Py_ssize_t"><code class="xref c c-type docutils literal notranslate">Py_ssize_t</code></a>]</dt><dd>Convert a Python integer to a C <a class="reference internal" href="intro.html#c.Py_ssize_t" title="Py_ssize_t"><code class="xref c c-type docutils literal notranslate">Py_ssize_t</code></a>.
</dd>
<dt><code class="docutils literal notranslate">c</code> (<a class="reference internal" href="../library/stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate">bytes</code></a> or <a class="reference internal" href="../library/stdtypes.html#bytearray" title="bytearray"><code class="xref py py-class docutils literal notranslate">bytearray</code></a> of length 1) [char]</dt><dd>Convert a Python byte, represented as a <a class="reference internal" href="../library/stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate">bytes</code></a> or
<a class="reference internal" href="../library/stdtypes.html#bytearray" title="bytearray"><code class="xref py py-class docutils literal notranslate">bytearray</code></a> object of length 1, to a C char.
<div class="versionchanged">
Changed in version 3.3: Allow <a class="reference internal" href="../library/stdtypes.html#bytearray" title="bytearray"><code class="xref py py-class docutils literal notranslate">bytearray</code></a> objects.
</div>
</dd>
<dt><code class="docutils literal notranslate">C</code> (<a class="reference internal" href="../library/stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a> of length 1) [int]</dt><dd>Convert a Python character, represented as a <a class="reference internal" href="../library/stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a> object of
length 1, to a C int.
</dd>
<dt><code class="docutils literal notranslate">f</code> (<a class="reference internal" href="../library/functions.html#float" title="float"><code class="xref py py-class docutils literal notranslate">float</code></a>) [float]</dt><dd>Convert a Python floating point number to a C float.
</dd>
<dt><code class="docutils literal notranslate">d</code> (<a class="reference internal" href="../library/functions.html#float" title="float"><code class="xref py py-class docutils literal notranslate">float</code></a>) [double]</dt><dd>Convert a Python floating point number to a C double.
</dd>
<dt><code class="docutils literal notranslate">D</code> (<a class="reference internal" href="../library/functions.html#complex" title="complex"><code class="xref py py-class docutils literal notranslate">complex</code></a>) [Py_complex]</dt><dd>Convert a Python complex number to a C <a class="reference internal" href="complex.html#c.Py_complex" title="Py_complex"><code class="xref c c-type docutils literal notranslate">Py_complex</code></a> structure.
</dd>
</dl>
</section>
<section id="other-objects">
<h3>Other objects<a class="headerlink" href="#other-objects" title="Permalink to this headline">¶</a></h3>
<dl class="simple">
<dt><code class="docutils literal notranslate">O</code> (object) [PyObject *]</dt><dd>Store a Python object (without any conversion) in a C object pointer. The C
program thus receives the actual object that was passed. The object’s reference
count is not increased. The pointer stored is not <code class="docutils literal notranslate">NULL</code>.
</dd>
<dt><code class="docutils literal notranslate">O!</code> (object) [typeobject, PyObject *]</dt><dd>Store a Python object in a C object pointer. This is similar to <code class="docutils literal notranslate">O</code>, but
takes two C arguments: the first is the address of a Python type object, the
second is the address of the C variable (of type <a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a>*) into which
the object pointer is stored. If the Python object does not have the required
type, <a class="reference internal" href="../library/exceptions.html#TypeError" title="TypeError"><code class="xref py py-exc docutils literal notranslate">TypeError</code></a> is raised.
</dd>
</dl>
<dl id="o-ampersand">
<dt><code class="docutils literal notranslate">O&amp;</code> (object) [converter, anything]</dt><dd>Convert a Python object to a C variable through a converter function. This
takes two arguments: the first is a function, the second is the address of a C
variable (of arbitrary type), converted to void*. The converter
function in turn is called as follows:
<div class="highlight-c notranslate"><div class="highlight"><pre>status = converter(object, address);
</pre></div>
</div>
where object is the Python object to be converted and address is the
void* argument that was passed to the <code class="docutils literal notranslate">PyArg_Parse*</code> function.
The returned status should be <code class="docutils literal notranslate">1</code> for a successful conversion and <code class="docutils literal notranslate">0</code> if
the conversion has failed. When the conversion fails, the converter function
should raise an exception and leave the content of address unmodified.
If the converter returns <code class="docutils literal notranslate">Py_CLEANUP_SUPPORTED</code>, it may get called a
second time if the argument parsing eventually fails, giving the converter a
chance to release any memory that it had already allocated. In this second
call, the object parameter will be <code class="docutils literal notranslate">NULL</code>; address will have the same value
as in the original call.
<div class="versionchanged">
Changed in version 3.1: <code class="docutils literal notranslate">Py_CLEANUP_SUPPORTED</code> was added.
</div>
</dd>
<dt><code class="docutils literal notranslate">p</code> (<a class="reference internal" href="../library/functions.html#bool" title="bool"><code class="xref py py-class docutils literal notranslate">bool</code></a>) [int]</dt><dd>Tests the value passed in for truth (a boolean predicate) and converts
the result to its equivalent C true/false integer value.
Sets the int to <code class="docutils literal notranslate">1</code> if the expression was true and <code class="docutils literal notranslate">0</code> if it was false.
This accepts any valid Python value. See <a class="reference internal" href="../library/stdtypes.html#truth">Truth Value Testing</a> for more
information about how Python tests values for truth.
<div class="versionadded">
New in version 3.3.
</div>
</dd>
<dt><code class="docutils literal notranslate">(items)</code> (<a class="reference internal" href="../library/stdtypes.html#tuple" title="tuple"><code class="xref py py-class docutils literal notranslate">tuple</code></a>) [matching-items]</dt><dd>The object must be a Python sequence whose length is the number of format units
in items. The C arguments must correspond to the individual format units in
items. Format units for sequences may be nested.
</dd>
</dl>
It is possible to pass “long” integers (integers whose value exceeds the
platform’s <code class="xref py py-const docutils literal notranslate">LONG_MAX</code>) however no proper range checking is done — the
most significant bits are silently truncated when the receiving field is too
small to receive the value (actually, the semantics are inherited from downcasts
in C — your mileage may vary).
A few other characters have a meaning in a format string. These may not occur
inside nested parentheses. They are:
<dl>
<dt><code class="docutils literal notranslate">|</code></dt><dd>Indicates that the remaining arguments in the Python argument list are optional.
The C variables corresponding to optional arguments should be initialized to
their default value — when an optional argument is not specified,
<a class="reference internal" href="#c.PyArg_ParseTuple" title="PyArg_ParseTuple"><code class="xref c c-func docutils literal notranslate">PyArg_ParseTuple()</code></a> does not touch the contents of the corresponding C
variable(s).
</dd>
<dt><code class="docutils literal notranslate">$</code></dt><dd><a class="reference internal" href="#c.PyArg_ParseTupleAndKeywords" title="PyArg_ParseTupleAndKeywords"><code class="xref c c-func docutils literal notranslate">PyArg_ParseTupleAndKeywords()</code></a> only:
Indicates that the remaining arguments in the Python argument list are
keyword-only. Currently, all keyword-only arguments must also be optional
arguments, so <code class="docutils literal notranslate">|</code> must always be specified before <code class="docutils literal notranslate">$</code> in the format
string.
<div class="versionadded">
New in version 3.3.
</div>
</dd>
<dt><code class="docutils literal notranslate">:</code></dt><dd>The list of format units ends here; the string after the colon is used as the
function name in error messages (the “associated value” of the exception that
<a class="reference internal" href="#c.PyArg_ParseTuple" title="PyArg_ParseTuple"><code class="xref c c-func docutils literal notranslate">PyArg_ParseTuple()</code></a> raises).
</dd>
<dt><code class="docutils literal notranslate">;</code></dt><dd>The list of format units ends here; the string after the semicolon is used as
the error message instead of the default error message. <code class="docutils literal notranslate">:</code> and <code class="docutils literal notranslate">;</code>
mutually exclude each other.
</dd>
</dl>
Note that any Python object references which are provided to the caller are
borrowed references; do not decrement their reference count!
Additional arguments passed to these functions must be addresses of variables
whose type is determined by the format string; these are used to store values
from the input tuple. There are a few cases, as described in the list of format
units above, where these parameters are used as input values; they should match
what is specified for the corresponding format unit in that case.
For the conversion to succeed, the arg object must match the format
and the format must be exhausted. On success, the
<code class="docutils literal notranslate">PyArg_Parse*</code> functions return true, otherwise they return
false and raise an appropriate exception. When the
<code class="docutils literal notranslate">PyArg_Parse*</code> functions fail due to conversion failure in one
of the format units, the variables at the addresses corresponding to that
and the following format units are left untouched.
</section>
<section id="api-functions">
<h3>API Functions<a class="headerlink" href="#api-functions" title="Permalink to this headline">¶</a></h3>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyArg_ParseTuple">
int PyArg_ParseTuple(<a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a> *args, const char *format, ...)<a class="headerlink" href="#c.PyArg_ParseTuple" title="Permalink to this definition">¶</a> </dt>
<dd> Part of the <a class="reference internal" href="stable.html#stable">Stable ABI</a>.Parse the parameters of a function that takes only positional parameters into
local variables. Returns true on success; on failure, it returns false and
raises the appropriate exception.
</dd></dl>

<dl class="c function">
<dt class="sig sig-object c" id="c.PyArg_VaParse">
int PyArg_VaParse(<a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a> *args, const char *format, va_list vargs)<a class="headerlink" href="#c.PyArg_VaParse" title="Permalink to this definition">¶</a> </dt>
<dd> Part of the <a class="reference internal" href="stable.html#stable">Stable ABI</a>.Identical to <a class="reference internal" href="#c.PyArg_ParseTuple" title="PyArg_ParseTuple"><code class="xref c c-func docutils literal notranslate">PyArg_ParseTuple()</code></a>, except that it accepts a va_list rather
than a variable number of arguments.
</dd></dl>

<dl class="c function">
<dt class="sig sig-object c" id="c.PyArg_ParseTupleAndKeywords">
int PyArg_ParseTupleAndKeywords(<a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a> *args, <a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a> *kw, const char *format, char *keywords[], ...)<a class="headerlink" href="#c.PyArg_ParseTupleAndKeywords" title="Permalink to this definition">¶</a> </dt>
<dd> Part of the <a class="reference internal" href="stable.html#stable">Stable ABI</a>.Parse the parameters of a function that takes both positional and keyword
parameters into local variables. The keywords argument is a
<code class="docutils literal notranslate">NULL</code>-terminated array of keyword parameter names. Empty names denote
<a class="reference internal" href="../glossary.html#positional-only-parameter">positional-only parameters</a>.
Returns true on success; on failure, it returns false and raises the
appropriate exception.
<div class="versionchanged">
Changed in version 3.6: Added support for <a class="reference internal" href="../glossary.html#positional-only-parameter">positional-only parameters</a>.
</div>
</dd></dl>

<dl class="c function">
<dt class="sig sig-object c" id="c.PyArg_VaParseTupleAndKeywords">
int PyArg_VaParseTupleAndKeywords(<a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a> *args, <a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a> *kw, const char *format, char *keywords[], va_list vargs)<a class="headerlink" href="#c.PyArg_VaParseTupleAndKeywords" title="Permalink to this definition">¶</a> </dt>
<dd> Part of the <a class="reference internal" href="stable.html#stable">Stable ABI</a>.Identical to <a class="reference internal" href="#c.PyArg_ParseTupleAndKeywords" title="PyArg_ParseTupleAndKeywords"><code class="xref c c-func docutils literal notranslate">PyArg_ParseTupleAndKeywords()</code></a>, except that it accepts a
va_list rather than a variable number of arguments.
</dd></dl>

<dl class="c function">
<dt class="sig sig-object c" id="c.PyArg_ValidateKeywordArguments">
int PyArg_ValidateKeywordArguments(<a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a>*)<a class="headerlink" href="#c.PyArg_ValidateKeywordArguments" title="Permalink to this definition">¶</a> </dt>
<dd> Part of the <a class="reference internal" href="stable.html#stable">Stable ABI</a>.Ensure that the keys in the keywords argument dictionary are strings. This
is only needed if <a class="reference internal" href="#c.PyArg_ParseTupleAndKeywords" title="PyArg_ParseTupleAndKeywords"><code class="xref c c-func docutils literal notranslate">PyArg_ParseTupleAndKeywords()</code></a> is not used, since the
latter already does this check.
<div class="versionadded">
New in version 3.2.
</div>
</dd></dl>

<dl class="c function">
<dt class="sig sig-object c" id="c.PyArg_Parse">
int PyArg_Parse(<a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a> *args, const char *format, ...)<a class="headerlink" href="#c.PyArg_Parse" title="Permalink to this definition">¶</a> </dt>
<dd> Part of the <a class="reference internal" href="stable.html#stable">Stable ABI</a>.Function used to deconstruct the argument lists of “old-style” functions —
these are functions which use the <code class="xref py py-const docutils literal notranslate">METH_OLDARGS</code> parameter parsing
method, which has been removed in Python 3. This is not recommended for use
in parameter parsing in new code, and most code in the standard interpreter
has been modified to no longer use this for that purpose. It does remain a
convenient way to decompose other tuples, however, and may continue to be
used for that purpose.
</dd></dl>

<dl class="c function">
<dt class="sig sig-object c" id="c.PyArg_UnpackTuple">
int PyArg_UnpackTuple(<a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a> *args, const char *name, <a class="reference internal" href="intro.html#c.Py_ssize_t" title="Py_ssize_t">Py_ssize_t</a> min, <a class="reference internal" href="intro.html#c.Py_ssize_t" title="Py_ssize_t">Py_ssize_t</a> max, ...)<a class="headerlink" href="#c.PyArg_UnpackTuple" title="Permalink to this definition">¶</a> </dt>
<dd> Part of the <a class="reference internal" href="stable.html#stable">Stable ABI</a>.A simpler form of parameter retrieval which does not use a format string to
specify the types of the arguments. Functions which use this method to retrieve
their parameters should be declared as <a class="reference internal" href="structures.html#METH_VARARGS" title="METH_VARARGS"><code class="xref py py-const docutils literal notranslate">METH_VARARGS</code></a> in function or
method tables. The tuple containing the actual parameters should be passed as
args; it must actually be a tuple. The length of the tuple must be at least
min and no more than max; min and max may be equal. Additional
arguments must be passed to the function, each of which should be a pointer to a
<a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a>* variable; these will be filled in with the values from
args; they will contain <a class="reference internal" href="../glossary.html#term-borrowed-reference">borrowed references</a>.
The variables which correspond
to optional parameters not given by args will not be filled in; these should
be initialized by the caller. This function returns true on success and false if
args is not a tuple or contains the wrong number of elements; an exception
will be set if there was a failure.
This is an example of the use of this function, taken from the sources for the
<code class="xref py py-mod docutils literal notranslate">_weakref</code> helper module for weak references:
<div class="highlight-c notranslate"><div class="highlight"><pre>static PyObject *
weakref_ref(PyObject *self, PyObject *args)
{
 PyObject *object;
 PyObject *callback = NULL;
 PyObject *result = NULL;

if (PyArg_UnpackTuple(args, &quot;ref&quot;, 1, 2, &amp;object, &amp;callback)) {
 result = PyWeakref_NewRef(object, callback);
 }
 return result;
}
</pre></div>
</div>
The call to <a class="reference internal" href="#c.PyArg_UnpackTuple" title="PyArg_UnpackTuple"><code class="xref c c-func docutils literal notranslate">PyArg_UnpackTuple()</code></a> in this example is entirely equivalent to
this call to <a class="reference internal" href="#c.PyArg_ParseTuple" title="PyArg_ParseTuple"><code class="xref c c-func docutils literal notranslate">PyArg_ParseTuple()</code></a>:
<div class="highlight-c notranslate"><div class="highlight"><pre>PyArg_ParseTuple(args, &quot;O|O:ref&quot;, &amp;object, &amp;callback)
</pre></div>
</div>
</dd></dl>

</section>
</section>
<section id="building-values">
<h2>Building values<a class="headerlink" href="#building-values" title="Permalink to this headline">¶</a></h2>
<dl class="c function">
<dt class="sig sig-object c" id="c.Py_BuildValue">
<a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a> *Py_BuildValue(const char *format, ...)<a class="headerlink" href="#c.Py_BuildValue" title="Permalink to this definition">¶</a> </dt>
<dd>Return value: New reference. Part of the <a class="reference internal" href="stable.html#stable">Stable ABI</a>.Create a new value based on a format string similar to those accepted by the
<code class="docutils literal notranslate">PyArg_Parse*</code> family of functions and a sequence of values. Returns
the value or <code class="docutils literal notranslate">NULL</code> in the case of an error; an exception will be raised if
<code class="docutils literal notranslate">NULL</code> is returned.
<a class="reference internal" href="#c.Py_BuildValue" title="Py_BuildValue"><code class="xref c c-func docutils literal notranslate">Py_BuildValue()</code></a> 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 class="docutils literal notranslate">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.
When memory buffers are passed as parameters to supply data to build objects, as
for the <code class="docutils literal notranslate">s</code> and <code class="docutils literal notranslate">s#</code> formats, the required data is copied. Buffers provided
by the caller are never referenced by the objects created by
<a class="reference internal" href="#c.Py_BuildValue" title="Py_BuildValue"><code class="xref c c-func docutils literal notranslate">Py_BuildValue()</code></a>. In other words, if your code invokes <code class="xref c c-func docutils literal notranslate">malloc()</code>
and passes the allocated memory to <a class="reference internal" href="#c.Py_BuildValue" title="Py_BuildValue"><code class="xref c c-func docutils literal notranslate">Py_BuildValue()</code></a>, your code is
responsible for calling <code class="xref c c-func docutils literal notranslate">free()</code> for that memory once
<a class="reference internal" href="#c.Py_BuildValue" title="Py_BuildValue"><code class="xref c c-func docutils literal notranslate">Py_BuildValue()</code></a> returns.
In the following description, the quoted form is the format unit; the entry in
(round) parentheses is the Python object type that the format unit will return;
and the entry in [square] brackets is the type of the C value(s) to be passed.
The characters space, tab, colon and comma are ignored in format strings (but
not within format units such as <code class="docutils literal notranslate">s#</code>). This can be used to make long format
strings a tad more readable.
<dl class="simple">
<dt><code class="docutils literal notranslate">s</code> (<a class="reference internal" href="../library/stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a> or <code class="docutils literal notranslate">None</code>) [const char *]</dt><dd>Convert a null-terminated C string to a Python <a class="reference internal" href="../library/stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a> object using <code class="docutils literal notranslate">'utf-8'</code>
encoding. If the C string pointer is <code class="docutils literal notranslate">NULL</code>, <code class="docutils literal notranslate">None</code> is used.
</dd>
<dt><code class="docutils literal notranslate">s#</code> (<a class="reference internal" href="../library/stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a> or <code class="docutils literal notranslate">None</code>) [const char *, <a class="reference internal" href="intro.html#c.Py_ssize_t" title="Py_ssize_t"><code class="xref c c-type docutils literal notranslate">Py_ssize_t</code></a>]</dt><dd>Convert a C string and its length to a Python <a class="reference internal" href="../library/stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a> object using <code class="docutils literal notranslate">'utf-8'</code>
encoding. If the C string pointer is <code class="docutils literal notranslate">NULL</code>, the length is ignored and
<code class="docutils literal notranslate">None</code> is returned.
</dd>
<dt><code class="docutils literal notranslate">y</code> (<a class="reference internal" href="../library/stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate">bytes</code></a>) [const char *]</dt><dd>This converts a C string to a Python <a class="reference internal" href="../library/stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate">bytes</code></a> object. If the C
string pointer is <code class="docutils literal notranslate">NULL</code>, <code class="docutils literal notranslate">None</code> is returned.
</dd>
<dt><code class="docutils literal notranslate">y#</code> (<a class="reference internal" href="../library/stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate">bytes</code></a>) [const char *, <a class="reference internal" href="intro.html#c.Py_ssize_t" title="Py_ssize_t"><code class="xref c c-type docutils literal notranslate">Py_ssize_t</code></a>]</dt><dd>This converts a C string and its lengths to a Python object. If the C
string pointer is <code class="docutils literal notranslate">NULL</code>, <code class="docutils literal notranslate">None</code> is returned.
</dd>
<dt><code class="docutils literal notranslate">z</code> (<a class="reference internal" href="../library/stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a> or <code class="docutils literal notranslate">None</code>) [const char *]</dt><dd>Same as <code class="docutils literal notranslate">s</code>.
</dd>
<dt><code class="docutils literal notranslate">z#</code> (<a class="reference internal" href="../library/stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a> or <code class="docutils literal notranslate">None</code>) [const char *, <a class="reference internal" href="intro.html#c.Py_ssize_t" title="Py_ssize_t"><code class="xref c c-type docutils literal notranslate">Py_ssize_t</code></a>]</dt><dd>Same as <code class="docutils literal notranslate">s#</code>.
</dd>
<dt><code class="docutils literal notranslate">u</code> (<a class="reference internal" href="../library/stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a>) [const wchar_t *]</dt><dd>Convert a null-terminated wchar_t buffer of Unicode (UTF-16 or UCS-4)
data to a Python Unicode object. If the Unicode buffer pointer is <code class="docutils literal notranslate">NULL</code>,
<code class="docutils literal notranslate">None</code> is returned.
</dd>
<dt><code class="docutils literal notranslate">u#</code> (<a class="reference internal" href="../library/stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a>) [const wchar_t *, <a class="reference internal" href="intro.html#c.Py_ssize_t" title="Py_ssize_t"><code class="xref c c-type docutils literal notranslate">Py_ssize_t</code></a>]</dt><dd>Convert a Unicode (UTF-16 or UCS-4) data buffer and its length to a Python
Unicode object. If the Unicode buffer pointer is <code class="docutils literal notranslate">NULL</code>, the length is ignored
and <code class="docutils literal notranslate">None</code> is returned.
</dd>
<dt><code class="docutils literal notranslate">U</code> (<a class="reference internal" href="../library/stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a> or <code class="docutils literal notranslate">None</code>) [const char *]</dt><dd>Same as <code class="docutils literal notranslate">s</code>.
</dd>
<dt><code class="docutils literal notranslate">U#</code> (<a class="reference internal" href="../library/stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a> or <code class="docutils literal notranslate">None</code>) [const char *, <a class="reference internal" href="intro.html#c.Py_ssize_t" title="Py_ssize_t"><code class="xref c c-type docutils literal notranslate">Py_ssize_t</code></a>]</dt><dd>Same as <code class="docutils literal notranslate">s#</code>.
</dd>
<dt><code class="docutils literal notranslate">i</code> (<a class="reference internal" href="../library/functions.html#int" title="int"><code class="xref py py-class docutils literal notranslate">int</code></a>) [int]</dt><dd>Convert a plain C int to a Python integer object.
</dd>
<dt><code class="docutils literal notranslate">b</code> (<a class="reference internal" href="../library/functions.html#int" title="int"><code class="xref py py-class docutils literal notranslate">int</code></a>) [char]</dt><dd>Convert a plain C char to a Python integer object.
</dd>
<dt><code class="docutils literal notranslate">h</code> (<a class="reference internal" href="../library/functions.html#int" title="int"><code class="xref py py-class docutils literal notranslate">int</code></a>) [short int]</dt><dd>Convert a plain C short int to a Python integer object.
</dd>
<dt><code class="docutils literal notranslate">l</code> (<a class="reference internal" href="../library/functions.html#int" title="int"><code class="xref py py-class docutils literal notranslate">int</code></a>) [long int]</dt><dd>Convert a C long int to a Python integer object.
</dd>
<dt><code class="docutils literal notranslate">B</code> (<a class="reference internal" href="../library/functions.html#int" title="int"><code class="xref py py-class docutils literal notranslate">int</code></a>) [unsigned char]</dt><dd>Convert a C unsigned char to a Python integer object.
</dd>
<dt><code class="docutils literal notranslate">H</code> (<a class="reference internal" href="../library/functions.html#int" title="int"><code class="xref py py-class docutils literal notranslate">int</code></a>) [unsigned short int]</dt><dd>Convert a C unsigned short int to a Python integer object.
</dd>
<dt><code class="docutils literal notranslate">I</code> (<a class="reference internal" href="../library/functions.html#int" title="int"><code class="xref py py-class docutils literal notranslate">int</code></a>) [unsigned int]</dt><dd>Convert a C unsigned int to a Python integer object.
</dd>
<dt><code class="docutils literal notranslate">k</code> (<a class="reference internal" href="../library/functions.html#int" title="int"><code class="xref py py-class docutils literal notranslate">int</code></a>) [unsigned long]</dt><dd>Convert a C unsigned long to a Python integer object.
</dd>
<dt><code class="docutils literal notranslate">L</code> (<a class="reference internal" href="../library/functions.html#int" title="int"><code class="xref py py-class docutils literal notranslate">int</code></a>) [long long]</dt><dd>Convert a C long long to a Python integer object.
</dd>
<dt><code class="docutils literal notranslate">K</code> (<a class="reference internal" href="../library/functions.html#int" title="int"><code class="xref py py-class docutils literal notranslate">int</code></a>) [unsigned long long]</dt><dd>Convert a C unsigned long long to a Python integer object.
</dd>
<dt><code class="docutils literal notranslate">n</code> (<a class="reference internal" href="../library/functions.html#int" title="int"><code class="xref py py-class docutils literal notranslate">int</code></a>) [<a class="reference internal" href="intro.html#c.Py_ssize_t" title="Py_ssize_t"><code class="xref c c-type docutils literal notranslate">Py_ssize_t</code></a>]</dt><dd>Convert a C <a class="reference internal" href="intro.html#c.Py_ssize_t" title="Py_ssize_t"><code class="xref c c-type docutils literal notranslate">Py_ssize_t</code></a> to a Python integer.
</dd>
<dt><code class="docutils literal notranslate">c</code> (<a class="reference internal" href="../library/stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate">bytes</code></a> of length 1) [char]</dt><dd>Convert a C int representing a byte to a Python <a class="reference internal" href="../library/stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate">bytes</code></a> object of
length 1.
</dd>
<dt><code class="docutils literal notranslate">C</code> (<a class="reference internal" href="../library/stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a> of length 1) [int]</dt><dd>Convert a C int representing a character to Python <a class="reference internal" href="../library/stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a>
object of length 1.
</dd>
<dt><code class="docutils literal notranslate">d</code> (<a class="reference internal" href="../library/functions.html#float" title="float"><code class="xref py py-class docutils literal notranslate">float</code></a>) [double]</dt><dd>Convert a C double to a Python floating point number.
</dd>
<dt><code class="docutils literal notranslate">f</code> (<a class="reference internal" href="../library/functions.html#float" title="float"><code class="xref py py-class docutils literal notranslate">float</code></a>) [float]</dt><dd>Convert a C float to a Python floating point number.
</dd>
<dt><code class="docutils literal notranslate">D</code> (<a class="reference internal" href="../library/functions.html#complex" title="complex"><code class="xref py py-class docutils literal notranslate">complex</code></a>) [Py_complex *]</dt><dd>Convert a C <a class="reference internal" href="complex.html#c.Py_complex" title="Py_complex"><code class="xref c c-type docutils literal notranslate">Py_complex</code></a> structure to a Python complex number.
</dd>
<dt><code class="docutils literal notranslate">O</code> (object) [PyObject *]</dt><dd>Pass a Python object untouched (except for its reference count, which is
incremented by one). If the object passed in is a <code class="docutils literal notranslate">NULL</code> pointer, it is assumed
that this was caused because the call producing the argument found an error and
set an exception. Therefore, <a class="reference internal" href="#c.Py_BuildValue" title="Py_BuildValue"><code class="xref c c-func docutils literal notranslate">Py_BuildValue()</code></a> will return <code class="docutils literal notranslate">NULL</code> but won’t
raise an exception. If no exception has been raised yet, <a class="reference internal" href="../library/exceptions.html#SystemError" title="SystemError"><code class="xref py py-exc docutils literal notranslate">SystemError</code></a> is
set.
</dd>
<dt><code class="docutils literal notranslate">S</code> (object) [PyObject *]</dt><dd>Same as <code class="docutils literal notranslate">O</code>.
</dd>
<dt><code class="docutils literal notranslate">N</code> (object) [PyObject *]</dt><dd>Same as <code class="docutils literal notranslate">O</code>, except it doesn’t increment the reference count on the object.
Useful when the object is created by a call to an object constructor in the
argument list.
</dd>
<dt><code class="docutils literal notranslate">O&amp;</code> (object) [converter, anything]</dt><dd>Convert anything to a Python object through a converter function. The
function is called with anything (which should be compatible with void*)
as its argument and should return a “new” Python object, or <code class="docutils literal notranslate">NULL</code> if an
error occurred.
</dd>
<dt><code class="docutils literal notranslate">(items)</code> (<a class="reference internal" href="../library/stdtypes.html#tuple" title="tuple"><code class="xref py py-class docutils literal notranslate">tuple</code></a>) [matching-items]</dt><dd>Convert a sequence of C values to a Python tuple with the same number of items.
</dd>
<dt><code class="docutils literal notranslate">[items]</code> (<a class="reference internal" href="../library/stdtypes.html#list" title="list"><code class="xref py py-class docutils literal notranslate">list</code></a>) [matching-items]</dt><dd>Convert a sequence of C values to a Python list with the same number of items.
</dd>
<dt><code class="docutils literal notranslate">{items}</code> (<a class="reference internal" href="../library/stdtypes.html#dict" title="dict"><code class="xref py py-class docutils literal notranslate">dict</code></a>) [matching-items]</dt><dd>Convert a sequence of C values to a Python dictionary. Each pair of consecutive
C values adds one item to the dictionary, serving as key and value,
respectively.
</dd>
</dl>
If there is an error in the format string, the <a class="reference internal" href="../library/exceptions.html#SystemError" title="SystemError"><code class="xref py py-exc docutils literal notranslate">SystemError</code></a> exception is
set and <code class="docutils literal notranslate">NULL</code> returned.
</dd></dl>

<dl class="c function">
<dt class="sig sig-object c" id="c.Py_VaBuildValue">
<a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a> *Py_VaBuildValue(const char *format, va_list vargs)<a class="headerlink" href="#c.Py_VaBuildValue" title="Permalink to this definition">¶</a> </dt>
<dd>Return value: New reference. Part of the <a class="reference internal" href="stable.html#stable">Stable ABI</a>.Identical to <a class="reference internal" href="#c.Py_BuildValue" title="Py_BuildValue"><code class="xref c c-func docutils literal notranslate">Py_BuildValue()</code></a>, except that it accepts a va_list
rather than a variable number of arguments.
</dd></dl>

</section>
</section>

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 <ul>
<li><a class="reference internal" href="#">Parsing arguments and building values</a><ul>
<li><a class="reference internal" href="#parsing-arguments">Parsing arguments</a><ul>
<li><a class="reference internal" href="#strings-and-buffers">Strings and buffers</a></li>
<li><a class="reference internal" href="#numbers">Numbers</a></li>
<li><a class="reference internal" href="#other-objects">Other objects</a></li>
<li><a class="reference internal" href="#api-functions">API Functions</a></li>
</ul>
</li>
<li><a class="reference internal" href="#building-values">Building values</a></li>
</ul>
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