*NULL* on failure.

.. c:function:: PyObject* _PyObject_Vectorcall(PyObject *callable, PyObject *const *args, size_t nargsf, PyObject *kwnames)

Call a callable Python object *callable*, using

:c:data:`vectorcall <PyTypeObject.tp_vectorcall_offset>` if possible.

*args* is a C array with the positional arguments.

*nargsf* is the number of positional arguments plus optionally the flag

:const:`PY_VECTORCALL_ARGUMENTS_OFFSET` (see below).

To get actual number of arguments, use

:c:func:`PyVectorcall_NARGS(nargsf) <PyVectorcall_NARGS>`.

*kwnames* can be either NULL (no keyword arguments) or a tuple of keyword

names. In the latter case, the values of the keyword arguments are stored

in *args* after the positional arguments.

The number of keyword arguments does not influence *nargsf*.

*kwnames* must contain only objects of type ``str`` (not a subclass),

and all keys must be unique.

Return the result of the call on success, or *NULL* on failure.

This uses the vectorcall protocol if the callable supports it;

otherwise, the arguments are converted to use

:c:member:`~PyTypeObject.tp_call`.

.. note::

This function is provisional and expected to become public in Python 3.9,

with a different name and, possibly, changed semantics.

If you use the function, plan for updating your code for Python 3.9.

.. versionadded:: 3.8

.. c:var:: PY_VECTORCALL_ARGUMENTS_OFFSET

If set in a vectorcall *nargsf* argument, the callee is allowed to

temporarily change ``args[-1]``. In other words, *args* points to

argument 1 (not 0) in the allocated vector.

The callee must restore the value of ``args[-1]`` before returning.

Whenever they can do so cheaply (without additional allocation), callers

are encouraged to use :const:`PY_VECTORCALL_ARGUMENTS_OFFSET`.

Doing so will allow callables such as bound methods to make their onward

calls (which include a prepended *self* argument) cheaply.

.. versionadded:: 3.8

.. c:function:: Py_ssize_t PyVectorcall_NARGS(size_t nargsf)

Given a vectorcall *nargsf* argument, return the actual number of

arguments.

Currently equivalent to ``nargsf & ~PY_VECTORCALL_ARGUMENTS_OFFSET``.

.. versionadded:: 3.8

.. c:function:: PyObject* _PyObject_FastCallDict(PyObject *callable, PyObject *const *args, size_t nargsf, PyObject *kwdict)

Same as :c:func:`_PyObject_Vectorcall` except that the keyword arguments

are passed as a dictionary in *kwdict*. This may be *NULL* if there

are no keyword arguments.

For callables supporting :c:data:`vectorcall <PyTypeObject.tp_vectorcall_offset>`,

the arguments are internally converted to the vectorcall convention.

Therefore, this function adds some overhead compared to

:c:func:`_PyObject_Vectorcall`.

It should only be used if the caller already has a dictionary ready to use.

.. note::

This function is provisional and expected to become public in Python 3.9,

with a different name and, possibly, changed semantics.

If you use the function, plan for updating your code for Python 3.9.

.. versionadded:: 3.8

.. c:function:: Py_hash_t PyObject_Hash(PyObject *o)

.. index:: builtin: hash