Doc/c-api/arg.rst
.. highlight:: c
.. _arg-parsing:
These functions are useful when creating your own extension functions and
methods. Additional information and examples are available in
:ref:extending-index.
The first three of these functions described, :c:func:PyArg_ParseTuple,
:c:func:PyArg_ParseTupleAndKeywords, and :c:func:PyArg_Parse, 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.
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.
.. _arg-parsing-string-and-buffers:
.. note::
On Python 3.12 and older, the macro :c:macro:!PY_SSIZE_T_CLEAN must be
defined before including :file:Python.h to use all # variants of
formats (s#, y#, etc.) explained below.
This is not necessary on Python 3.13 and later.
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:
Formats such as y* and s* fill a :c:type:Py_buffer structure.
This locks the underlying buffer so that the caller can subsequently use
the buffer even inside a :c:type:Py_BEGIN_ALLOW_THREADS
block without the risk of mutable data being resized or destroyed.
As a result, you have to call :c:func:PyBuffer_Release after you have
finished processing the data (or in any early abort case).
The es, es#, et and et# formats allocate the result buffer.
You have to call :c:func:PyMem_Free after you have finished
processing the data (or in any early abort case).
.. _c-arg-borrowed-buffer:
Other formats take a :class:str or a read-only :term:bytes-like object,
such as :class:bytes, and provide a const char * 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
:c:member:PyBufferProcs.bf_releasebuffer field must be NULL.
This disallows common mutable objects such as :class:bytearray,
but also some read-only objects such as :class:memoryview of
:class:bytes.
Besides this bf_releasebuffer 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).
s (:class:str) [const char *]
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 :exc:ValueError exception is raised. Unicode objects are converted
to C strings using 'utf-8' encoding. If this conversion fails, a
:exc:UnicodeError is raised.
.. note::
This format does not accept :term:bytes-like objects <bytes-like object>. If you want to accept
filesystem paths and convert them to C character strings, it is
preferable to use the O& format with :c:func:PyUnicode_FSConverter
as converter.
.. versionchanged:: 3.5
Previously, :exc:TypeError was raised when embedded null code points
were encountered in the Python string.
s* (:class:str or :term:bytes-like object) [Py_buffer]
This format accepts Unicode objects as well as bytes-like objects.
It fills a :c:type:Py_buffer 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 'utf-8' encoding.
s# (:class:str, read-only :term:bytes-like object) [const char *, :c:type:Py_ssize_t]
Like s*, except that it provides a :ref:borrowed buffer <c-arg-borrowed-buffer>.
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 'utf-8' encoding.
z (:class:str or None) [const char *]
Like s, but the Python object may also be None, in which case the C
pointer is set to NULL.
z* (:class:str, :term:bytes-like object or None) [Py_buffer]
Like s*, but the Python object may also be None, in which case the
buf member of the :c:type:Py_buffer structure is set to NULL.
z# (:class:str, read-only :term:bytes-like object or None) [const char *, :c:type:Py_ssize_t]
Like s#, but the Python object may also be None, in which case the C
pointer is set to NULL.
y (read-only :term:bytes-like object) [const char *]
This format converts a bytes-like object to a C pointer to a
:ref:borrowed <c-arg-borrowed-buffer> character string;
it does not accept Unicode objects. The bytes buffer must not
contain embedded null bytes; if it does, a :exc:ValueError
exception is raised.
.. versionchanged:: 3.5
Previously, :exc:TypeError was raised when embedded null bytes were
encountered in the bytes buffer.
y* (:term:bytes-like object) [Py_buffer]
This variant on s* doesn't accept Unicode objects, only
bytes-like objects. This is the recommended way to accept
binary data.
y# (read-only :term:bytes-like object) [const char *, :c:type:Py_ssize_t]
This variant on s# doesn't accept Unicode objects, only bytes-like
objects.
S (:class:bytes) [PyBytesObject *]
Requires that the Python object is a :class:bytes object, without
attempting any conversion. Raises :exc:TypeError if the object is not
a bytes object. The C variable may also be declared as :c:expr:PyObject*.
Y (:class:bytearray) [PyByteArrayObject *]
Requires that the Python object is a :class:bytearray object, without
attempting any conversion. Raises :exc:TypeError if the object is not
a :class:bytearray object. The C variable may also be declared as :c:expr:PyObject*.
U (:class:str) [PyObject *]
Requires that the Python object is a Unicode object, without attempting
any conversion. Raises :exc:TypeError if the object is not a Unicode
object. The C variable may also be declared as :c:expr:PyObject*.
w* (read-write :term:bytes-like object) [Py_buffer]
This format accepts any object which implements the read-write buffer
interface. It fills a :c:type:Py_buffer structure provided by the caller.
The buffer may contain embedded null bytes. The caller has to call
:c:func:PyBuffer_Release when it is done with the buffer.
es (:class:str) [const char *encoding, char **buffer]
This variant on s 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 :c:expr:const char* which points to the name of an encoding as a
NUL-terminated string, or NULL, in which case 'utf-8' encoding is used.
An exception is raised if the named encoding is not known to Python. The
second argument must be a :c:expr: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.
:c:func:PyArg_ParseTuple 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 :c:func:PyMem_Free to
free the allocated buffer after use.
et (:class:str, :class:bytes or :class:bytearray) [const char *encoding, char **buffer]
Same as es 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.
es# (:class:str) [const char *encoding, char **buffer, :c:type:Py_ssize_t *buffer_length]
This variant on s# is used for encoding Unicode into a character buffer.
Unlike the es 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
:c:expr:const char* which points to the name of an encoding as a
NUL-terminated string, or NULL, in which case 'utf-8' encoding is used.
An exception is raised if the named encoding is not known to Python. The
second argument must be a :c:expr: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 NULL 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
:c:func:PyMem_Free to free the allocated buffer after usage.
If *buffer points to a non-NULL pointer (an already allocated buffer),
:c:func:PyArg_ParseTuple 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 :exc:ValueError will be set.
In both cases, *buffer_length is set to the length of the encoded data without the trailing NUL byte.
et# (:class:str, :class:bytes or :class:bytearray) [const char *encoding, char **buffer, :c:type:Py_ssize_t *buffer_length]
Same as es# 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.
.. versionchanged:: 3.12
u, u#, Z, and Z# are removed because they used a legacy
Py_UNICODE* representation.
These formats allow representing Python numbers or single characters as C numbers.
Formats that require :class:int, :class:float or :class:complex can
also use the corresponding special methods :meth:~object.__index__,
:meth:~object.__float__ or :meth:~object.__complex__ to convert
the Python object to the required type.
For signed integer formats, :exc:OverflowError is raised if the value
is out of range for the C type.
For unsigned integer formats, the
most significant bits are silently truncated when the receiving field is too
small to receive the value, and :exc:DeprecationWarning is emitted when
the value is larger than the maximal value for the C type or less than
the minimal value for the corresponding signed integer type of the same size.
b (:class:int) [unsigned char]
Convert a nonnegative Python integer to an unsigned tiny integer, stored in a C
:c:expr:unsigned char.
B (:class:int) [unsigned char]
Convert a Python integer to a tiny integer without overflow checking, stored in a C
:c:expr:unsigned char.
Convert a Python integer to a C :c:expr:unsigned char.
h (:class:int) [short int]
Convert a Python integer to a C :c:expr:short int.
H (:class:int) [unsigned short int]
Convert a Python integer to a C :c:expr:unsigned short int.
i (:class:int) [int]
Convert a Python integer to a plain C :c:expr:int.
I (:class:int) [unsigned int]
Convert a Python integer to a C :c:expr:unsigned int.
l (:class:int) [long int]
Convert a Python integer to a C :c:expr:long int.
k (:class:int) [unsigned long]
Convert a Python integer to a C :c:expr:unsigned long.
.. versionchanged:: 3.14
Use :meth:~object.__index__ if available.
L (:class:int) [long long]
Convert a Python integer to a C :c:expr:long long.
K (:class:int) [unsigned long long]
Convert a Python integer to a C :c:expr:unsigned long long.
.. versionchanged:: 3.14
Use :meth:~object.__index__ if available.
n (:class:int) [:c:type:Py_ssize_t]
Convert a Python integer to a C :c:type:Py_ssize_t.
c (:class:bytes or :class:bytearray of length 1) [char]
Convert a Python byte, represented as a :class:bytes or
:class:bytearray object of length 1, to a C :c:expr:char.
.. versionchanged:: 3.3
Allow :class:bytearray objects.
C (:class:str of length 1) [int]
Convert a Python character, represented as a :class:str object of
length 1, to a C :c:expr:int.
f (:class:float) [float]
Convert a Python floating-point number to a C :c:expr:float.
d (:class:float) [double]
Convert a Python floating-point number to a C :c:expr:double.
D (:class:complex) [Py_complex]
Convert a Python complex number to a C :c:type:Py_complex structure.
.. deprecated:: 3.15
For unsigned integer formats B, H, I, k and K,
:exc:DeprecationWarning is emitted when the value is larger than
the maximal value for the C type or less than the minimal value for
the corresponding signed integer type of the same size.
O (object) [PyObject *]
Store a Python object (without any conversion) in a C object pointer. The C
program thus receives the actual object that was passed. A new
:term:strong reference to the object is not created
(i.e. its reference count is not increased).
The pointer stored is not NULL.
O! (object) [typeobject, PyObject *]
Store a Python object in a C object pointer. This is similar to O, 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 :c:expr:PyObject*) into which
the object pointer is stored. If the Python object does not have the required
type, :exc:TypeError is raised.
.. _o_ampersand:
O& (object) [converter, address]
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 :c:expr:void *. The converter
function in turn is called as follows::
status = converter(object, address);
where object is the Python object to be converted and address is the
:c:expr:void* argument that was passed to the PyArg_Parse* function.
The returned status should be 1 for a successful conversion and 0 if
the conversion has failed. When the conversion fails, the converter function
should raise an exception and leave the content of address unmodified.
.. c:macro:: Py_CLEANUP_SUPPORTED :no-typesetting:
If the converter returns :c:macro:!Py_CLEANUP_SUPPORTED, 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 NULL; address will have the same value
as in the original call.
Examples of converters: :c:func:PyUnicode_FSConverter and
:c:func:PyUnicode_FSDecoder.
.. versionchanged:: 3.1
:c:macro:!Py_CLEANUP_SUPPORTED was added.
p (:class:bool) [int]
Tests the value passed in for truth (a boolean p\ redicate) and converts
the result to its equivalent C true/false integer value.
Sets the int to 1 if the expression was true and 0 if it was false.
This accepts any valid Python value. See :ref:truth for more
information about how Python tests values for truth.
.. versionadded:: 3.3
(items) (sequence) [matching-items]
The object must be a Python sequence (except :class:str, :class:bytes
or :class:bytearray) 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.
If items contains format units which store a :ref:borrowed buffer <c-arg-borrowed-buffer> (s, s#, z, z#, y, or y#)
or a :term:borrowed reference (S, Y, U, O, or O!),
the object must be a Python tuple.
The converter for the O& format unit in items must not store
a borrowed buffer or a borrowed reference.
.. versionchanged:: 3.14
:class:str and :class:bytearray objects no longer accepted as a sequence.
.. deprecated:: 3.14 Non-tuple sequences are deprecated if items contains format units which store a borrowed buffer or a borrowed reference.
A few other characters have a meaning in a format string. These may not occur inside nested parentheses. They are:
|
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,
:c:func:PyArg_ParseTuple does not touch the contents of the corresponding C
variable(s).
$
:c:func:PyArg_ParseTupleAndKeywords 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 | must always be specified before $ in the format
string.
.. versionadded:: 3.3
:
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
:c:func:PyArg_ParseTuple raises).
;
The list of format units ends here; the string after the semicolon is used as
the error message instead of the default error message. : and ;
mutually exclude each other.
Note that any Python object references which are provided to the caller are borrowed references; do not release them (i.e. 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
PyArg_Parse* functions return true, otherwise they return
false and raise an appropriate exception. When the
PyArg_Parse* 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.
.. c:function:: int PyArg_ParseTuple(PyObject *args, const char *format, ...)
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.
.. c:function:: int PyArg_VaParse(PyObject *args, const char *format, va_list vargs)
Identical to :c:func:PyArg_ParseTuple, except that it accepts a va_list rather
than a variable number of arguments.
.. c:function:: int PyArg_ParseTupleAndKeywords(PyObject *args, PyObject *kw, const char *format, char * const *keywords, ...)
Parse the parameters of a function that takes both positional and keyword
parameters into local variables.
The keywords argument is a NULL-terminated array of keyword parameter
names specified as null-terminated ASCII or UTF-8 encoded C strings.
Empty names denote
:ref:positional-only parameters <positional-only_parameter>.
Returns true on success; on failure, it returns false and raises the
appropriate exception.
.. note::
The *keywords* parameter declaration is :c:expr:`char * const *` in C and
:c:expr:`const char * const *` in C++.
This can be overridden with the :c:macro:`PY_CXX_CONST` macro.
.. versionchanged:: 3.6
Added support for :ref:positional-only parameters <positional-only_parameter>.
.. versionchanged:: 3.13
The keywords parameter has now type :c:expr:char * const * in C and
:c:expr:const char * const * in C++, instead of :c:expr:char **.
Added support for non-ASCII keyword parameter names.
.. c:function:: int PyArg_VaParseTupleAndKeywords(PyObject *args, PyObject *kw, const char *format, char * const *keywords, va_list vargs)
Identical to :c:func:PyArg_ParseTupleAndKeywords, except that it accepts a
va_list rather than a variable number of arguments.
.. c:function:: int PyArg_ValidateKeywordArguments(PyObject *)
Ensure that the keys in the keywords argument dictionary are strings. This
is only needed if :c:func:PyArg_ParseTupleAndKeywords is not used, since the
latter already does this check.
.. versionadded:: 3.2
.. c:function:: int PyArg_Parse(PyObject *args, const char *format, ...)
Parse the parameter of a function that takes a single positional parameter into a local variable. Returns true on success; on failure, it returns false and raises the appropriate exception.
Example::
// Function using METH_O calling convention
static PyObject*
my_function(PyObject *module, PyObject *arg)
{
int value;
if (!PyArg_Parse(arg, "i:my_function", &value)) {
return NULL;
}
// ... use value ...
}
.. c:function:: int PyArg_ParseArray(PyObject *const *args, Py_ssize_t nargs, const char *format, ...)
Parse the parameters of a function that takes only array parameters into
local variables (that is, a function using the :c:macro:METH_FASTCALL
calling convention).
Returns true on success; on failure, it returns false and raises the
appropriate exception.
.. versionadded:: 3.15
.. c:function:: int PyArg_ParseArrayAndKeywords(PyObject *const *args, Py_ssize_t nargs, PyObject *kwnames, const char *format, const char * const *kwlist, ...)
Parse the parameters of a function that takes both array and keyword
parameters into local variables (that is, a function using the
:c:macro:METH_FASTCALL | :c:macro:METH_KEYWORDS calling convention).
Returns true on success; on failure, it returns false and raises the
appropriate exception.
.. versionadded:: 3.15
.. c:function:: int PyArg_UnpackTuple(PyObject *args, const char *name, Py_ssize_t min, Py_ssize_t max, ...)
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 :c:macro:METH_VARARGS 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
:c:expr:PyObject* variable; these will be filled in with the values from
args; they will contain :term:borrowed references <borrowed reference>.
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
:mod:!_weakref helper module for weak references::
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;
}
The call to :c:func:PyArg_UnpackTuple in this example is entirely equivalent to
this call to :c:func:PyArg_ParseTuple::
PyArg_ParseTuple(args, "O|O:ref", &object, &callback)
.. c:macro:: PY_CXX_CONST
The value to be inserted, if any, before :c:expr:char * const *
in the keywords parameter declaration of
:c:func:PyArg_ParseTupleAndKeywords and
:c:func:PyArg_VaParseTupleAndKeywords.
Default empty for C and const for C++
(:c:expr:const char * const *).
To override, define it to the desired value before including
:file:Python.h.
.. versionadded:: 3.13
.. c:function:: PyObject* Py_BuildValue(const char *format, ...)
Create a new value based on a format string similar to those accepted by the
PyArg_Parse* family of functions and a sequence of values. Returns
the value or NULL in the case of an error; an exception will be raised if
NULL is returned.
:c:func:Py_BuildValue 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 None; 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 s and s# formats, the required data is copied. Buffers provided
by the caller are never referenced by the objects created by
:c:func:Py_BuildValue. In other words, if your code invokes :c:func:malloc
and passes the allocated memory to :c:func:Py_BuildValue, your code is
responsible for calling :c:func:free for that memory once
:c:func:Py_BuildValue 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 s#). This can be used to make long format
strings a tad more readable.
s (:class:str or None) [const char *]
Convert a null-terminated C string to a Python :class:str object using 'utf-8'
encoding. If the C string pointer is NULL, None is used.
s# (:class:str or None) [const char *, :c:type:Py_ssize_t]
Convert a C string and its length to a Python :class:str object using 'utf-8'
encoding. If the C string pointer is NULL, the length is ignored and
None is returned.
y (:class:bytes) [const char *]
This converts a C string to a Python :class:bytes object. If the C
string pointer is NULL, None is returned.
y# (:class:bytes) [const char *, :c:type:Py_ssize_t]
This converts a C string and its lengths to a Python object. If the C
string pointer is NULL, None is returned.
z (:class:str or None) [const char *]
Same as s.
z# (:class:str or None) [const char *, :c:type:Py_ssize_t]
Same as s#.
u (:class:str) [const wchar_t *]
Convert a null-terminated :c:type:wchar_t buffer of Unicode (UTF-16 or UCS-4)
data to a Python Unicode object. If the Unicode buffer pointer is NULL,
None is returned.
u# (:class:str) [const wchar_t *, :c:type:Py_ssize_t]
Convert a Unicode (UTF-16 or UCS-4) data buffer and its length to a Python
Unicode object. If the Unicode buffer pointer is NULL, the length is ignored
and None is returned.
U (:class:str or None) [const char *]
Same as s.
U# (:class:str or None) [const char *, :c:type:Py_ssize_t]
Same as s#.
i (:class:int) [int]
Convert a plain C :c:expr:int to a Python integer object.
b (:class:int) [char]
Convert a plain C :c:expr:char to a Python integer object.
h (:class:int) [short int]
Convert a plain C :c:expr:short int to a Python integer object.
l (:class:int) [long int]
Convert a C :c:expr:long int to a Python integer object.
B (:class:int) [unsigned char]
Convert a C :c:expr:unsigned char to a Python integer object.
H (:class:int) [unsigned short int]
Convert a C :c:expr:unsigned short int to a Python integer object.
I (:class:int) [unsigned int]
Convert a C :c:expr:unsigned int to a Python integer object.
k (:class:int) [unsigned long]
Convert a C :c:expr:unsigned long to a Python integer object.
L (:class:int) [long long]
Convert a C :c:expr:long long to a Python integer object.
.. _capi-py-buildvalue-format-K:
K (:class:int) [unsigned long long]
Convert a C :c:expr:unsigned long long to a Python integer object.
n (:class:int) [:c:type:Py_ssize_t]
Convert a C :c:type:Py_ssize_t to a Python integer.
p (:class:bool) [int]
Convert a C :c:expr:int to a Python :class:bool object.
Be aware that this format requires an ``int`` argument.
Unlike most other contexts in C, variadic arguments are not coerced to
a suitable type automatically.
You can convert another type (for example, a pointer or a float) to a
suitable ``int`` value using ``(x) ? 1 : 0`` or ``!!x``.
.. versionadded:: 3.14
c (:class:bytes of length 1) [char]
Convert a C :c:expr:int representing a byte to a Python :class:bytes object of
length 1.
C (:class:str of length 1) [int]
Convert a C :c:expr:int representing a character to Python :class:str
object of length 1.
d (:class:float) [double]
Convert a C :c:expr:double to a Python floating-point number.
f (:class:float) [float]
Convert a C :c:expr:float to a Python floating-point number.
D (:class:complex) [Py_complex *]
Convert a C :c:type:Py_complex structure to a Python complex number.
O (object) [PyObject *]
Pass a Python object untouched but create a new
:term:strong reference to it
(i.e. its reference count is incremented by one).
If the object passed in is a NULL pointer, it is assumed
that this was caused because the call producing the argument found an error and
set an exception. Therefore, :c:func:Py_BuildValue will return NULL but won't
raise an exception. If no exception has been raised yet, :exc:SystemError is
set.
S (object) [PyObject *]
Same as O.
N (object) [PyObject *]
Same as O, except it doesn't create a new :term:strong reference.
Useful when the object is created by a call to an object constructor in the
argument list.
O& (object) [converter, anything]
Convert anything to a Python object through a converter function. The
function is called with anything (which should be compatible with :c:expr:void*)
as its argument and should return a "new" Python object, or NULL if an
error occurred.
(items) (:class:tuple) [matching-items]
Convert a sequence of C values to a Python tuple with the same number of items.
[items] (:class:list) [matching-items]
Convert a sequence of C values to a Python list with the same number of items.
{items} (:class:dict) [matching-items]
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.
If there is an error in the format string, the :exc:SystemError exception is
set and NULL returned.
.. c:function:: PyObject* Py_VaBuildValue(const char *format, va_list vargs)
Identical to :c:func:Py_BuildValue, except that it accepts a va_list
rather than a variable number of arguments.