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<H1><A NAME="SECTION007500000000000000000"></A><A NAME="arg-parsing"></A>
<BR>
5.5 Parsing arguments and building values
</H1>
<P>
These functions are useful when creating your own extensions functions
and methods. Additional information and examples are available in
<em class="citetitle"><a
href="../ext/ext.html"
title="Extending and Embedding the Python
Interpreter"
>Extending and Embedding the Python
Interpreter</a></em>.
<P>
The first three of these functions described,
<tt class="cfunction">PyArg_ParseTuple()</tt>,
<tt class="cfunction">PyArg_ParseTupleAndKeywords()</tt>, and
<tt class="cfunction">PyArg_Parse()</tt>, all use <em>format strings</em> which are
used to tell the function about the expected arguments. The format
strings use the same syntax for each of these functions.
<P>
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.
<P>
<DL>
<DT><STRONG>"<tt class="samp">s</tt>" (string or Unicode object) [const char *]</STRONG></DT>
<DD>Convert a Python string or Unicode object to a C pointer to a
character string. You must not provide storage for the string
itself; a pointer to an existing string is stored into the character
pointer variable whose address you pass. The C string is
NUL-terminated. The Python string must not contain embedded NUL
bytes; if it does, a <tt class="exception">TypeError</tt> exception is raised.
Unicode objects are converted to C strings using the default
encoding. If this conversion fails, a <tt class="exception">UnicodeError</tt> is
raised.
<P>
</DD>
<DT><STRONG>"<tt class="samp">s#</tt>" (string, Unicode or any read buffer compatible object)
[const char *, int]</STRONG></DT>
<DD>This variant on "<tt class="samp">s</tt>" stores into two C variables, the first one
a pointer to a character string, the second one its length. In this
case the Python string may contain embedded null bytes. Unicode
objects pass back a pointer to the default encoded string version of
the object if such a conversion is possible. All other read-buffer
compatible objects pass back a reference to the raw internal data
representation.
<P>
</DD>
<DT><STRONG>"<tt class="samp">z</tt>" (string or <code>None</code>) [const char *]</STRONG></DT>
<DD>Like "<tt class="samp">s</tt>", but the Python object may also be <code>None</code>, in
which case the C pointer is set to <tt class="constant">NULL</tt>.
<P>
</DD>
<DT><STRONG>"<tt class="samp">z#</tt>" (string or <code>None</code> or any read buffer
compatible object) [const char *, int]</STRONG></DT>
<DD>This is to "<tt class="samp">s#</tt>" as "<tt class="samp">z</tt>" is to "<tt class="samp">s</tt>".
<P>
</DD>
<DT><STRONG>"<tt class="samp">u</tt>" (Unicode object) [Py_UNICODE *]</STRONG></DT>
<DD>Convert a Python Unicode object to a C pointer to a NUL-terminated
buffer of 16-bit Unicode (UTF-16) data. As with "<tt class="samp">s</tt>", there is
no need to provide storage for the Unicode data buffer; a pointer to
the existing Unicode data is stored into the <tt class="ctype">Py_UNICODE</tt>
pointer variable whose address you pass.
<P>
</DD>
<DT><STRONG>"<tt class="samp">u#</tt>" (Unicode object) [Py_UNICODE *, int]</STRONG></DT>
<DD>This variant on "<tt class="samp">u</tt>" stores into two C variables, the first one
a pointer to a Unicode data buffer, the second one its length.
Non-Unicode objects are handled by interpreting their read-buffer
pointer as pointer to a <tt class="ctype">Py_UNICODE</tt> array.
<P>
</DD>
<DT><STRONG>"<tt class="samp">es</tt>" (string, Unicode object or character buffer
compatible object) [const char *encoding, char **buffer]</STRONG></DT>
<DD>This variant on "<tt class="samp">s</tt>" is used for encoding Unicode and objects
convertible to Unicode into a character buffer. It only works for
encoded data without embedded NUL bytes.
<P>
This format requires two arguments. The first is only used as
input, and must be a <tt class="ctype">const char*</tt> which points to the name of an
encoding as a NUL-terminated string, or <tt class="constant">NULL</tt>, in which case the
default encoding is used. An exception is raised if the named
encoding is not known to Python. The second argument must be a
<tt class="ctype">char**</tt>; 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.
<P>
<tt class="cfunction">PyArg_ParseTuple()</tt> will allocate a buffer of the needed
size, copy the encoded data into this buffer and adjust
<var>*buffer</var> to reference the newly allocated storage. The caller
is responsible for calling <tt class="cfunction">PyMem_Free()</tt> to free the
allocated buffer after use.
<P>
</DD>
<DT><STRONG>"<tt class="samp">et</tt>" (string, Unicode object or character buffer
compatible object) [const char *encoding, char **buffer]</STRONG></DT>
<DD>Same as "<tt class="samp">es</tt>" except that 8-bit string objects are passed
through without recoding them. Instead, the implementation assumes
that the string object uses the encoding passed in as parameter.
<P>
</DD>
<DT><STRONG>"<tt class="samp">es#</tt>" (string, Unicode object or character buffer compatible
object) [const char *encoding, char **buffer, int *buffer_length]</STRONG></DT>
<DD>This variant on "<tt class="samp">s#</tt>" is used for encoding Unicode and objects
convertible to Unicode into a character buffer. Unlike the
"<tt class="samp">es</tt>" format, this variant allows input data which contains NUL
characters.
<P>
It requires three arguments. The first is only used as input, and
must be a <tt class="ctype">const char*</tt> which points to the name of an encoding as a
NUL-terminated string, or <tt class="constant">NULL</tt>, in which case the default encoding
is used. An exception is raised if the named encoding is not known
to Python. The second argument must be a <tt class="ctype">char**</tt>; 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.
<P>
There are two modes of operation:
<P>
If <var>*buffer</var> points a <tt class="constant">NULL</tt> pointer, the function will
allocate a buffer of the needed size, copy the encoded data into
this buffer and set <var>*buffer</var> to reference the newly allocated
storage. The caller is responsible for calling
<tt class="cfunction">PyMem_Free()</tt> to free the allocated buffer after usage.
<P>
If <var>*buffer</var> points to a non-<tt class="constant">NULL</tt> pointer (an already
allocated buffer), <tt class="cfunction">PyArg_ParseTuple()</tt> will use this
location as the buffer and interpret the initial value of
<var>*buffer_length</var> 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 <tt class="exception">ValueError</tt> will be set.
<P>
In both cases, <var>*buffer_length</var> is set to the length of the
encoded data without the trailing NUL byte.
<P>
</DD>
<DT><STRONG>"<tt class="samp">et#</tt>" (string, Unicode object or character buffer compatible
object) [const char *encoding, char **buffer]</STRONG></DT>
<DD>Same as "<tt class="samp">es#</tt>" except that string objects are passed through
without recoding them. Instead, the implementation assumes that the
string object uses the encoding passed in as parameter.
<P>
</DD>
<DT><STRONG>"<tt class="samp">b</tt>" (integer) [char]</STRONG></DT>
<DD>Convert a Python integer to a tiny int, stored in a C <tt class="ctype">char</tt>.
<P>
</DD>
<DT><STRONG>"<tt class="samp">B</tt>" (integer) [unsigned char]</STRONG></DT>
<DD>Convert a Python integer to a tiny int without overflow checking,
stored in a C <tt class="ctype">unsigned char</tt>.
<span class="versionnote">New in version 2.3.</span>
<P>
</DD>
<DT><STRONG>"<tt class="samp">h</tt>" (integer) [short int]</STRONG></DT>
<DD>Convert a Python integer to a C <tt class="ctype">short int</tt>.
<P>
</DD>
<DT><STRONG>"<tt class="samp">H</tt>" (integer) [unsigned short int]</STRONG></DT>
<DD>Convert a Python integer to a C <tt class="ctype">unsigned short int</tt>, without
overflow checking.
<span class="versionnote">New in version 2.3.</span>
<P>
</DD>
<DT><STRONG>"<tt class="samp">i</tt>" (integer) [int]</STRONG></DT>
<DD>Convert a Python integer to a plain C <tt class="ctype">int</tt>.
<P>
</DD>
<DT><STRONG>"<tt class="samp">I</tt>" (integer) [unsigned int]</STRONG></DT>
<DD>Convert a Python integer to a C <tt class="ctype">unsigned int</tt>, without
overflow checking.
<span class="versionnote">New in version 2.3.</span>
<P>
</DD>
<DT><STRONG>"<tt class="samp">l</tt>" (integer) [long int]</STRONG></DT>
<DD>Convert a Python integer to a C <tt class="ctype">long int</tt>.
<P>
</DD>
<DT><STRONG>"<tt class="samp">k</tt>" (integer) [unsigned long]</STRONG></DT>
<DD>Convert a Python integer or long integer to a C <tt class="ctype">unsigned long</tt> without
overflow checking.
<span class="versionnote">New in version 2.3.</span>
<P>
</DD>
<DT><STRONG>"<tt class="samp">L</tt>" (integer) [PY_LONG_LONG]</STRONG></DT>
<DD>Convert a Python integer to a C <tt class="ctype">long long</tt>. This format is
only available on platforms that support <tt class="ctype">long long</tt> (or
<tt class="ctype">_int64</tt> on Windows).
<P>
</DD>
<DT><STRONG>"<tt class="samp">K</tt>" (integer) [unsigned PY_LONG_LONG]</STRONG></DT>
<DD>Convert a Python integer or long integer to a C <tt class="ctype">unsigned long long</tt>
without overflow checking. This format is only available on
platforms that support <tt class="ctype">unsigned long long</tt> (or
<tt class="ctype">unsigned _int64</tt> on Windows).
<span class="versionnote">New in version 2.3.</span>
<P>
</DD>
<DT><STRONG>"<tt class="samp">c</tt>" (string of length 1) [char]</STRONG></DT>
<DD>Convert a Python character, represented as a string of length 1, to
a C <tt class="ctype">char</tt>.
<P>
</DD>
<DT><STRONG>"<tt class="samp">f</tt>" (float) [float]</STRONG></DT>
<DD>Convert a Python floating point number to a C <tt class="ctype">float</tt>.
<P>
</DD>
<DT><STRONG>"<tt class="samp">d</tt>" (float) [double]</STRONG></DT>
<DD>Convert a Python floating point number to a C <tt class="ctype">double</tt>.
<P>
</DD>
<DT><STRONG>"<tt class="samp">D</tt>" (complex) [Py_complex]</STRONG></DT>
<DD>Convert a Python complex number to a C <tt class="ctype">Py_complex</tt> structure.
<P>
</DD>
<DT><STRONG>"<tt class="samp">O</tt>" (object) [PyObject *]</STRONG></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 <tt class="constant">NULL</tt>.
<P>
</DD>
<DT><STRONG>"<tt class="samp">O!</tt>" (object) [<var>typeobject</var>, PyObject *]</STRONG></DT>
<DD>Store a Python object in a C object pointer. This is similar to
"<tt class="samp">O</tt>", 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 <tt class="ctype">PyObject*</tt>) into which the object pointer is stored. If
the Python object does not have the required type,
<tt class="exception">TypeError</tt> is raised.
<P>
</DD>
<DT><STRONG>"<tt class="samp">O&</tt>" (object) [<var>converter</var>, <var>anything</var>]</STRONG></DT>
<DD>Convert a Python object to a C variable through a <var>converter</var>
function. This takes two arguments: the first is a function, the
second is the address of a C variable (of arbitrary type), converted
to <tt class="ctype">void *</tt>. The <var>converter</var> function in turn is called
as follows:
<P>
<var>status</var><code> = </code><var>converter</var><code>(</code><var>object</var>,
<var>address</var><code>);</code>
<P>
where <var>object</var> is the Python object to be converted and
<var>address</var> is the <tt class="ctype">void*</tt> argument that was passed to the
<tt class="cfunction">PyArg_Parse*()</tt> function. The returned <var>status</var>
should be <code>1</code> for a successful conversion and <code>0</code> if the
conversion has failed. When the conversion fails, the
<var>converter</var> function should raise an exception.
<P>
</DD>
<DT><STRONG>"<tt class="samp">S</tt>" (string) [PyStringObject *]</STRONG></DT>
<DD>Like "<tt class="samp">O</tt>" but requires that the Python object is a string
object. Raises <tt class="exception">TypeError</tt> if the object is not a string
object. The C variable may also be declared as <tt class="ctype">PyObject*</tt>.
<P>
</DD>
<DT><STRONG>"<tt class="samp">U</tt>" (Unicode string) [PyUnicodeObject *]</STRONG></DT>
<DD>Like "<tt class="samp">O</tt>" but requires that the Python object is a Unicode
object. Raises <tt class="exception">TypeError</tt> if the object is not a Unicode
object. The C variable may also be declared as <tt class="ctype">PyObject*</tt>.
<P>
</DD>
<DT><STRONG>"<tt class="samp">t#</tt>" (read-only character buffer) [char *, int]</STRONG></DT>
<DD>Like "<tt class="samp">s#</tt>", but accepts any object which implements the
read-only buffer interface. The <tt class="ctype">char*</tt> variable is set to
point to the first byte of the buffer, and the <tt class="ctype">int</tt> is set to
the length of the buffer. Only single-segment buffer objects are
accepted; <tt class="exception">TypeError</tt> is raised for all others.
<P>
</DD>
<DT><STRONG>"<tt class="samp">w</tt>" (read-write character buffer) [char *]</STRONG></DT>
<DD>Similar to "<tt class="samp">s</tt>", but accepts any object which implements the
read-write buffer interface. The caller must determine the length
of the buffer by other means, or use "<tt class="samp">w#</tt>" instead. Only
single-segment buffer objects are accepted; <tt class="exception">TypeError</tt> is
raised for all others.
<P>
</DD>
<DT><STRONG>"<tt class="samp">w#</tt>" (read-write character buffer) [char *, int]</STRONG></DT>
<DD>Like "<tt class="samp">s#</tt>", but accepts any object which implements the
read-write buffer interface. The <tt class="ctype">char *</tt> variable is set to
point to the first byte of the buffer, and the <tt class="ctype">int</tt> is set to
the length of the buffer. Only single-segment buffer objects are
accepted; <tt class="exception">TypeError</tt> is raised for all others.
<P>
</DD>
<DT><STRONG>"<tt class="samp">(<var>items</var>)</tt>" (tuple) [<var>matching-items</var>]</STRONG></DT>
<DD>The object must be a Python sequence whose length is the number of
format units in <var>items</var>. The C arguments must correspond to the
individual format units in <var>items</var>. Format units for sequences
may be nested.
<P>
<span class="note"><b class="label">Note:</b>
Prior to Python version 1.5.2, this format specifier only
accepted a tuple containing the individual parameters, not an
arbitrary sequence. Code which previously caused
<tt class="exception">TypeError</tt> to be raised here may now proceed without an
exception. This is not expected to be a problem for existing code.</span>
</DD>
</DL>
<P>
It is possible to pass Python long integers where integers are
requested; 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).
<P>
A few other characters have a meaning in a format string. These may
not occur inside nested parentheses. They are:
<P>
<DL>
<DT><STRONG>"<tt class="samp">|</tt>"</STRONG></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, <tt class="cfunction">PyArg_ParseTuple()</tt> does not
touch the contents of the corresponding C variable(s).
<P>
</DD>
<DT><STRONG>"<tt class="samp">:</tt>"</STRONG></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 <tt class="cfunction">PyArg_ParseTuple()</tt>
raises).
<P>
</DD>
<DT><STRONG>"<tt class="samp">;</tt>"</STRONG></DT>
<DD>The list of format units ends here; the string after the semicolon
is used as the error message <em>instead</em> of the default error
message. Clearly, "<tt class="samp">:</tt>" and "<tt class="samp">;</tt>" mutually exclude each
other.
</DD>
</DL>
<P>
Note that any Python object references which are provided to the
caller are <em>borrowed</em> references; do not decrement their
reference count!
<P>
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.
<P>
For the conversion to succeed, the <var>arg</var> object must match the
format and the format must be exhausted. On success, the
<tt class="cfunction">PyArg_Parse*()</tt> functions return true, otherwise they
return false and raise an appropriate exception.
<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"><td><nobr>int <b><tt id='l2h-208' xml:id='l2h-208' class="cfunction">PyArg_ParseTuple</tt></b>(</nobr></td><td>PyObject *<var>args</var>, char *<var>format</var>,
...)</td></tr></table></dt>
<dd>
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>
<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"><td><nobr>int <b><tt id='l2h-209' xml:id='l2h-209' class="cfunction">PyArg_VaParse</tt></b>(</nobr></td><td>PyObject *<var>args</var>, char *<var>format</var>,
va_list <var>vargs</var>)</td></tr></table></dt>
<dd>
Identical to <tt class="cfunction">PyArg_ParseTuple()</tt>, except that it accepts a
va_list rather than a variable number of arguments.
</dd></dl>
<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"><td><nobr>int <b><tt id='l2h-210' xml:id='l2h-210' class="cfunction">PyArg_ParseTupleAndKeywords</tt></b>(</nobr></td><td>PyObject *<var>args</var>,
PyObject *<var>kw</var>, char *<var>format</var>, char *keywords[],
...)</td></tr></table></dt>
<dd>
Parse the parameters of a function that takes both positional and
keyword parameters into local variables. Returns true on success;
on failure, it returns false and raises the appropriate exception.
</dd></dl>
<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"><td><nobr>int <b><tt id='l2h-211' xml:id='l2h-211' class="cfunction">PyArg_VaParseTupleAndKeywords</tt></b>(</nobr></td><td>PyObject *<var>args</var>,
PyObject *<var>kw</var>, char *<var>format</var>, char *keywords[],
va_list <var>vargs</var>)</td></tr></table></dt>
<dd>
Identical to <tt class="cfunction">PyArg_ParseTupleAndKeywords()</tt>, except that it
accepts a va_list rather than a variable number of arguments.
</dd></dl>
<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"><td><nobr>int <b><tt id='l2h-212' xml:id='l2h-212' class="cfunction">PyArg_Parse</tt></b>(</nobr></td><td>PyObject *<var>args</var>, char *<var>format</var>,
...)</td></tr></table></dt>
<dd>
Function used to deconstruct the argument lists of ``old-style''
functions -- these are functions which use the
<tt class="constant">METH_OLDARGS</tt> parameter parsing method. 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>
<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"><td><nobr>int <b><tt id='l2h-213' xml:id='l2h-213' class="cfunction">PyArg_UnpackTuple</tt></b>(</nobr></td><td>PyObject *<var>args</var>, char *<var>name</var>,
int <var>min</var>, int <var>max</var>, ...)</td></tr></table></dt>
<dd>
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
<tt class="constant">METH_VARARGS</tt> in function or method tables. The tuple
containing the actual parameters should be passed as <var>args</var>; it
must actually be a tuple. The length of the tuple must be at least
<var>min</var> and no more than <var>max</var>; <var>min</var> and <var>max</var> may be
equal. Additional arguments must be passed to the function, each of
which should be a pointer to a <tt class="ctype">PyObject*</tt> variable; these
will be filled in with the values from <var>args</var>; they will contain
borrowed references. The variables which correspond to optional
parameters not given by <var>args</var> will not be filled in; these
should be initialized by the caller.
This function returns true on success and false if <var>args</var> is not
a tuple or contains the wrong number of elements; an exception will
be set if there was a failure.
<P>
This is an example of the use of this function, taken from the
sources for the <tt class="module">_weakref</tt> helper module for weak references:
<P>
<div class="verbatim"><pre>
static PyObject *
weakref_ref(PyObject *self, PyObject *args)
{
PyObject *object;
PyObject *callback = NULL;
PyObject *result = NULL;
if (PyArg_UnpackTuple(args, "ref", 1, 2, &object, &callback)) {
result = PyWeakref_NewRef(object, callback);
}
return result;
}
</pre></div>
<P>
The call to <tt class="cfunction">PyArg_UnpackTuple()</tt> in this example is
entirely equivalent to this call to <tt class="cfunction">PyArg_ParseTuple()</tt>:
<P>
<div class="verbatim"><pre>
PyArg_ParseTuple(args, "O|O:ref", &object, &callback)
</pre></div>
<P>
<span class="versionnote">New in version 2.2.</span>
</dd></dl>
<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"><td><nobr>PyObject* <b><tt id='l2h-214' xml:id='l2h-214' class="cfunction">Py_BuildValue</tt></b>(</nobr></td><td>char *<var>format</var>,
...)</td></tr></table></dt>
<dd>
<div class="refcount-info">
<span class="label">Return value:</span>
<span class="value">New reference.</span>
</div>
Create a new value based on a format string similar to those
accepted by the <tt class="cfunction">PyArg_Parse*()</tt> family of functions and a
sequence of values. Returns the value or <tt class="constant">NULL</tt> in the case of an
error; an exception will be raised if <tt class="constant">NULL</tt> is returned.
<P>
<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>
When memory buffers are passed as parameters to supply data to build
objects, as for the "<tt class="samp">s</tt>" and "<tt class="samp">s#</tt>" formats, the required
data is copied. Buffers provided by the caller are never referenced
by the objects created by <tt class="cfunction">Py_BuildValue()</tt>. In other
words, if your code invokes <tt class="cfunction">malloc()</tt> and passes the
allocated memory to <tt class="cfunction">Py_BuildValue()</tt>, your code is
responsible for calling <tt class="cfunction">free()</tt> for that memory once
<tt class="cfunction">Py_BuildValue()</tt> returns.
<P>
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.
<P>
The characters space, tab, colon and comma are ignored in format
strings (but not within format units such as "<tt class="samp">s#</tt>"). This can
be used to make long format strings a tad more readable.
<P>
<DL>
<DT><STRONG>"<tt class="samp">s</tt>" (string) [char *]</STRONG></DT>
<DD>Convert a null-terminated C string to a Python object. If the C
string pointer is <tt class="constant">NULL</tt>, <code>None</code> is used.
<P>
</DD>
<DT><STRONG>"<tt class="samp">s#</tt>" (string) [char *, int]</STRONG></DT>
<DD>Convert a C string and its length to a Python object. If the C
string pointer is <tt class="constant">NULL</tt>, the length is ignored and <code>None</code> is
returned.
<P>
</DD>
<DT><STRONG>"<tt class="samp">z</tt>" (string or <code>None</code>) [char *]</STRONG></DT>
<DD>Same as "<tt class="samp">s</tt>".
<P>
</DD>
<DT><STRONG>"<tt class="samp">z#</tt>" (string or <code>None</code>) [char *, int]</STRONG></DT>
<DD>Same as "<tt class="samp">s#</tt>".
<P>
</DD>
<DT><STRONG>"<tt class="samp">u</tt>" (Unicode string) [Py_UNICODE *]</STRONG></DT>
<DD>Convert a null-terminated buffer of Unicode (UCS-2 or UCS-4)
data to a Python Unicode object. If the Unicode buffer pointer
is <tt class="constant">NULL</tt>, <code>None</code> is returned.
<P>
</DD>
<DT><STRONG>"<tt class="samp">u#</tt>" (Unicode string) [Py_UNICODE *, int]</STRONG></DT>
<DD>Convert a Unicode (UCS-2 or UCS-4) data buffer and its length
to a Python Unicode object. If the Unicode buffer pointer
is <tt class="constant">NULL</tt>, the length is ignored and <code>None</code> is returned.
<P>
</DD>
<DT><STRONG>"<tt class="samp">i</tt>" (integer) [int]</STRONG></DT>
<DD>Convert a plain C <tt class="ctype">int</tt> to a Python integer object.
<P>
</DD>
<DT><STRONG>"<tt class="samp">b</tt>" (integer) [char]</STRONG></DT>
<DD>Convert a plain C <tt class="ctype">char</tt> to a Python integer object.
<P>
</DD>
<DT><STRONG>"<tt class="samp">h</tt>" (integer) [short int]</STRONG></DT>
<DD>Convert a plain C <tt class="ctype">short int</tt> to a Python integer object.
<P>
</DD>
<DT><STRONG>"<tt class="samp">l</tt>" (integer) [long int]</STRONG></DT>
<DD>Convert a C <tt class="ctype">long int</tt> to a Python integer object.
<P>
</DD>
<DT><STRONG>"<tt class="samp">B</tt>" (integer) [unsigned char]</STRONG></DT>
<DD>Convert a C <tt class="ctype">unsigned char</tt> to a Python integer object.
<P>
</DD>
<DT><STRONG>"<tt class="samp">H</tt>" (integer) [unsigned short int]</STRONG></DT>
<DD>Convert a C <tt class="ctype">unsigned short int</tt> to a Python integer object.
<P>
</DD>
<DT><STRONG>"<tt class="samp">I</tt>" (integer/long) [unsigned int]</STRONG></DT>
<DD>Convert a C <tt class="ctype">unsigned int</tt> to a Python integer object
or a Python long integer object, if it is larger than <code>sys.maxint</code>.
<P>
</DD>
<DT><STRONG>"<tt class="samp">k</tt>" (integer/long) [unsigned long]</STRONG></DT>
<DD>Convert a C <tt class="ctype">unsigned long</tt> to a Python integer object
or a Python long integer object, if it is larger than <code>sys.maxint</code>.
<P>
</DD>
<DT><STRONG>"<tt class="samp">L</tt>" (long) [PY_LONG_LONG]</STRONG></DT>
<DD>Convert a C <tt class="ctype">long long</tt> to a Python long integer object. Only
available on platforms that support <tt class="ctype">long long</tt>.
<P>
</DD>
<DT><STRONG>"<tt class="samp">K</tt>" (long) [unsigned PY_LONG_LONG]</STRONG></DT>
<DD>Convert a C <tt class="ctype">unsigned long long</tt> to a Python long integer object.
Only available on platforms that support <tt class="ctype">unsigned long long</tt>.
<P>
</DD>
<DT><STRONG>"<tt class="samp">c</tt>" (string of length 1) [char]</STRONG></DT>
<DD>Convert a C <tt class="ctype">int</tt> representing a character to a Python
string of length 1.
<P>
</DD>
<DT><STRONG>"<tt class="samp">d</tt>" (float) [double]</STRONG></DT>
<DD>Convert a C <tt class="ctype">double</tt> to a Python floating point number.
<P>
</DD>
<DT><STRONG>"<tt class="samp">f</tt>" (float) [float]</STRONG></DT>
<DD>Same as "<tt class="samp">d</tt>".
<P>
</DD>
<DT><STRONG>"<tt class="samp">D</tt>" (complex) [Py_complex *]</STRONG></DT>
<DD>Convert a C <tt class="ctype">Py_complex</tt> structure to a Python complex
number.
<P>
</DD>
<DT><STRONG>"<tt class="samp">O</tt>" (object) [PyObject *]</STRONG></DT>
<DD>Pass a Python object untouched (except for its reference count,
which is incremented by one). If the object passed in is a
<tt class="constant">NULL</tt> pointer, it is assumed that this was caused because the
call producing the argument found an error and set an exception.
Therefore, <tt class="cfunction">Py_BuildValue()</tt> will return <tt class="constant">NULL</tt> but
won't raise an exception. If no exception has been raised yet,
<tt class="exception">SystemError</tt> is set.
<P>
</DD>
<DT><STRONG>"<tt class="samp">S</tt>" (object) [PyObject *]</STRONG></DT>
<DD>Same as "<tt class="samp">O</tt>".
<P>
</DD>
<DT><STRONG>"<tt class="samp">N</tt>" (object) [PyObject *]</STRONG></DT>
<DD>Same as "<tt class="samp">O</tt>", 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.
<P>
</DD>
<DT><STRONG>"<tt class="samp">O&</tt>" (object) [<var>converter</var>, <var>anything</var>]</STRONG></DT>
<DD>Convert <var>anything</var> to a Python object through a
<var>converter</var> function. The function is called with
<var>anything</var> (which should be compatible with <tt class="ctype">void *</tt>) as
its argument and should return a ``new'' Python object, or <tt class="constant">NULL</tt>
if an error occurred.
<P>
</DD>
<DT><STRONG>"<tt class="samp">(<var>items</var>)</tt>" (tuple) [<var>matching-items</var>]</STRONG></DT>
<DD>Convert a sequence of C values to a Python tuple with the same
number of items.
<P>
</DD>
<DT><STRONG>"<tt class="samp">[<var>items</var>]</tt>" (list) [<var>matching-items</var>]</STRONG></DT>
<DD>Convert a sequence of C values to a Python list with the same
number of items.
<P>
</DD>
<DT><STRONG>"<tt class="samp">{<var>items</var>}</tt>" (dictionary) [<var>matching-items</var>]</STRONG></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.
<P>
</DD>
</DL>
<P>
If there is an error in the format string, the
<tt class="exception">SystemError</tt> exception is set and <tt class="constant">NULL</tt> returned.
</dd></dl>
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