python_doc_md/Advanced/c-api/function.md

Function Objects

::: index pair: object; function :::

There are a few functions specific to Python functions.

The C structure used for functions.

::: index single: MethodType (in module types) :::

This is an instance of PyTypeObject{.interpreted-text role="c:type"} and represents the Python function type. It is exposed to Python programmers as types.FunctionType.

Return true if o is a function object (has type PyFunction_Type{.interpreted-text role="c:data"}). The parameter must not be NULL. This function always succeeds.

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. ~function.__module__{.interpreted-text role="attr"} is retrieved from globals. The argument defaults, annotations and closure are set to NULL. ~function.__qualname__{.interpreted-text role="attr"} is set to the same value as the code object's ~codeobject.co_qualname{.interpreted-text role="attr"} field.

As PyFunction_New{.interpreted-text role="c:func"}, but also allows setting the function object's ~function.__qualname__{.interpreted-text role="attr"} attribute. qualname should be a unicode object or NULL; if NULL, the !__qualname__{.interpreted-text role="attr"} attribute is set to the same value as the code object's ~codeobject.co_qualname{.interpreted-text role="attr"} field.

::: versionadded 3.3 :::

Return the code object associated with the function object op.

Return the globals dictionary associated with the function object op.

Return a borrowed reference{.interpreted-text role="term"} to the ~function.__module__{.interpreted-text role="attr"} attribute of the function object <user-defined-funcs>{.interpreted-text role="ref"} op. It can be NULL.

This is normally a string <str>{.interpreted-text role="class"} containing the module name, but can be set to any other object by Python code.

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

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

Raises SystemError{.interpreted-text role="exc"} and returns -1 on failure.

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!

::: versionadded 3.12 :::

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

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.

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

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

Raises SystemError{.interpreted-text role="exc"} and returns -1 on failure.

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

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

Raises SystemError{.interpreted-text role="exc"} and returns -1 on failure.

Register callback as a function watcher for the current interpreter. Return an ID which may be passed to PyFunction_ClearWatcher{.interpreted-text role="c:func"}. In case of error (e.g. no more watcher IDs available), return -1 and set an exception.

::: versionadded 3.12 :::

Clear watcher identified by watcher_id previously returned from PyFunction_AddWatcher{.interpreted-text role="c:func"} 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.)

::: versionadded 3.12 :::

Enumeration of possible function watcher events:

• PyFunction_EVENT_CREATE
• PyFunction_EVENT_DESTROY
• PyFunction_EVENT_MODIFY_CODE
• PyFunction_EVENT_MODIFY_DEFAULTS
• PyFunction_EVENT_MODIFY_KWDEFAULTS

::: versionadded 3.12 :::

• PyFunction_PYFUNC_EVENT_MODIFY_QUALNAME

::: versionadded 3.15 :::

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{.interpreted-text role="term"} 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{.interpreted-text role="c:func"}. 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.

::: versionadded 3.12 :::