# Function Objects

There are a few functions specific to Python functions.

type PyFunctionObject

  The C structure used for functions.

PyTypeObject PyFunction_Type

  This is an instance of `PyTypeObject` and represents the Python function type. It is exposed to Python programmers as `types.FunctionType`.

int PyFunction_Check(PyObject *o)

  Return true if o is a function object (has type `PyFunction_Type`). The parameter must not be `NULL`. This function always succeeds.

PyObject *PyFunction_New(PyObject *code, PyObject *globals)
  Return value: New reference.

  Return a new function object associated with the code object code. globals must be a dictionary with the global variables accessible to the function.

  The function’s docstring and name are retrieved from the code object. `__module__` is retrieved from globals. The argument defaults, annotations and closure are set to `NULL`. `__qualname__` is set to the same value as the code object’s `co_qualname` field.

PyObject *PyFunction_NewWithQualName(PyObject *code, PyObject *globals, PyObject *qualname)
  Return value: New reference.

  As `PyFunction_New()`, but also allows setting the function object’s `__qualname__` attribute. qualname should be a unicode object or `NULL`; if `NULL`, the `__qualname__` attribute is set to the same value as the code object’s `co_qualname` field.

  Added in version 3.3.

PyObject *PyFunction_GetCode(PyObject *op)
  Return value: Borrowed reference.

  Return the code object associated with the function object op.

PyObject *PyFunction_GetGlobals(PyObject *op)
  Return value: Borrowed reference.

  Return the globals dictionary associated with the function object op.

PyObject *PyFunction_GetModule(PyObject *op)
  Return value: Borrowed reference.

  Return a borrowed reference to the `__module__` attribute of the function object op. It can be NULL.

  This is normally a `string` containing the module name, but can be set to any other object by Python code.

PyObject *PyFunction_GetDefaults(PyObject *op)
  Return value: Borrowed reference.

  Return the argument default values of the function object op. This can be a tuple of arguments or `NULL`.

int PyFunction_SetDefaults(PyObject *op, PyObject *defaults)

  Set the argument default values for the function object op. defaults must be `Py_None` or a tuple.

  Raises `SystemError` and returns `-1` on failure.

void PyFunction_SetVectorcall(PyFunctionObject *func, vectorcallfunc vectorcall)

  Set the vectorcall field of a given function object func.

  Warning: extensions using this API must preserve the behavior of the unaltered (default) vectorcall function!

  Added in version 3.12.

PyObject *PyFunction_GetKwDefaults(PyObject *op)
  Return value: Borrowed reference.

  Return the keyword-only argument default values of the function object op. This can be a dictionary of arguments or `NULL`.

PyObject *PyFunction_GetClosure(PyObject *op)
  Return value: Borrowed reference.

  Return the closure associated with the function object op. This can be `NULL` or a tuple of cell objects.

int PyFunction_SetClosure(PyObject *op, PyObject *closure)

  Set the closure associated with the function object op. closure must be `Py_None` or a tuple of cell objects.

  Raises `SystemError` and returns `-1` on failure.

PyObject *PyFunction_GetAnnotations(PyObject *op)
  Return value: Borrowed reference.

  Return the annotations of the function object op. This can be a mutable dictionary or `NULL`.

int PyFunction_SetAnnotations(PyObject *op, PyObject *annotations)

  Set the annotations for the function object op. annotations must be a dictionary or `Py_None`.

  Raises `SystemError` and returns `-1` on failure.

PyObject *PyFunction_GET_CODE(PyObject *op)
PyObject *PyFunction_GET_GLOBALS(PyObject *op)
PyObject *PyFunction_GET_MODULE(PyObject *op)
PyObject *PyFunction_GET_DEFAULTS(PyObject *op)
PyObject *PyFunction_GET_KW_DEFAULTS(PyObject *op)
PyObject *PyFunction_GET_CLOSURE(PyObject *op)
PyObject *PyFunction_GET_ANNOTATIONS(PyObject *op)
  Return value: Borrowed reference.

  These functions are similar to their `PyFunction_Get*` counterparts, but do not do type checking. Passing anything other than an instance of `PyFunction_Type` is undefined behavior.

int PyFunction_AddWatcher(PyFunction_WatchCallback callback)

  Register callback as a function watcher for the current interpreter. Return an ID which may be passed to `PyFunction_ClearWatcher()`. In case of error (e.g. no more watcher IDs available), return `-1` and set an exception.

  Added in version 3.12.

int PyFunction_ClearWatcher(int watcher_id)

  Clear watcher identified by watcher_id previously returned from `PyFunction_AddWatcher()` for the current interpreter. Return `0` on success, or `-1` and set an exception on error (e.g. if the given watcher_id was never registered.)

  Added in version 3.12.

type PyFunction_WatchEvent

  > Enumeration of possible function watcher events:

  > - `PyFunction_EVENT_CREATE`

  > - `PyFunction_EVENT_DESTROY`

  > - `PyFunction_EVENT_MODIFY_CODE`

  > - `PyFunction_EVENT_MODIFY_DEFAULTS`

  > - `PyFunction_EVENT_MODIFY_KWDEFAULTS`

  Added in version 3.12.

typedef int (*PyFunction_WatchCallback)(PyFunction_WatchEvent event, PyFunctionObject *func, PyObject *new_value)

  Type of a function watcher callback function.

  If event is `PyFunction_EVENT_CREATE` or `PyFunction_EVENT_DESTROY` then new_value will be `NULL`. Otherwise, new_value will hold a borrowed reference to the new value that is about to be stored in func for the attribute that is being modified.

  The callback may inspect but must not modify func; doing so could have unpredictable effects, including infinite recursion.

  If event is `PyFunction_EVENT_CREATE`, then the callback is invoked after func has been fully initialized. Otherwise, the callback is invoked before the modification to func takes place, so the prior state of func can be inspected. The runtime is permitted to optimize away the creation of function objects when possible. In such cases no event will be emitted. Although this creates the possibility of an observable difference of runtime behavior depending on optimization decisions, it does not change the semantics of the Python code being executed.

  If event is `PyFunction_EVENT_DESTROY`, Taking a reference in the callback to the about-to-be-destroyed function will resurrect it, preventing it from being freed at this time. When the resurrected object is destroyed later, any watcher callbacks active at that time will be called again.

  If the callback sets an exception, it must return `-1`; this exception will be printed as an unraisable exception using `PyErr_WriteUnraisable()`. Otherwise it should return `0`.

  There may already be a pending exception set on entry to the callback. In this case, the callback should return `0` with the same exception still set. This means the callback may not call any other API that can set an exception unless it saves and clears the exception state first, and restores it before returning.

  Added in version 3.12.