Function Objects¶

There are a few functions specific to Python functions.

type PyFunctionObject¶

The C structure used for functions.

In the free-threaded build, direct access to mutable fields requires synchronization if another thread may modify the function. See C API Extension Support for Free Threading.

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.

In the free-threaded build, if the attribute may be modified concurrently, convert the borrowed reference to a strong reference with Py_XNewRef() immediately, before calling any other Python API. The same applies to PyFunction_GET_MODULE().

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.

int PyFunction_SetKwDefaults(PyObject *op, PyObject *defaults)¶

Set the keyword-only argument default values of the function object op. defaults must be a dictionary of keyword-only arguments or Py_None.

This function returns 0 on success, and returns -1 with an exception set on failure.

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:

• PyFunction_EVENT_MODIFY_QUALNAME

Added in version 3.15.

PY_FOREACH_FUNC_EVENT(V)¶

Apply the macro V to each suffix of PyFunction_WatchEvent constants. Currently expands to V(CREATE) V(DESTROY) V(MODIFY_CODE) V(MODIFY_DEFAULTS) V(MODIFY_KWDEFAULTS) V(MODIFY_QUALNAME). The macro V must accept one event name and supply any punctuation needed between expansions.

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.