Refer to Providing a C API for an Extension Module for more information on using these objects.
New in version 3.1.
PyCapsule
PyObject
represents an opaque value, useful for C extension modules who need to pass an opaque value (as a void*
pointer) through Python code to other C code. It is often used to make a C function pointer defined in one module available to other modules, so the regular import mechanism can be used to access C APIs defined in dynamically loaded modules.PyCapsule_Destructor
The type of a destructor callback for a capsule. Defined as:
typedef void (*PyCapsule_Destructor)(PyObject *);
See PyCapsule_New()
for the semantics of PyCapsule_Destructor
callbacks.
PyCapsule_New
(void *pointer, const char *name, PyCapsule_Destructor destructor)Return value: New reference.
Create a PyCapsule
encapsulating the pointer. The pointer
argument may not be NULL
.
On failure, set an exception and return NULL
.
The name string may either be NULL
or a pointer to a valid C string. If
non-NULL
, this string must outlive the capsule. (Though it is permitted to
free it inside the destructor.)
If the destructor argument is not NULL
, it will be called with the
capsule as its argument when it is destroyed.
If this capsule will be stored as an attribute of a module, the name should
be specified as modulename.attributename
. This will enable other modules
to import the capsule using PyCapsule_Import()
.
PyCapsule_GetPointer
(PyObject *capsule, const char *name)Retrieve the pointer stored in the capsule. On failure, set an exception
and return NULL
.
The name parameter must compare exactly to the name stored in the capsule.
If the name stored in the capsule is NULL
, the name passed in must also
be NULL
. Python uses the C function strcmp()
to compare capsule
names.
PyCapsule_GetDestructor
(PyObject *capsule)Return the current destructor stored in the capsule. On failure, set an
exception and return NULL
.
It is legal for a capsule to have a NULL
destructor. This makes a NULL
return code somewhat ambiguous; use PyCapsule_IsValid()
or
PyErr_Occurred()
to disambiguate.
PyCapsule_GetContext
(PyObject *capsule)Return the current context stored in the capsule. On failure, set an
exception and return NULL
.
It is legal for a capsule to have a NULL
context. This makes a NULL
return code somewhat ambiguous; use PyCapsule_IsValid()
or
PyErr_Occurred()
to disambiguate.
PyCapsule_GetName
(PyObject *capsule)Return the current name stored in the capsule. On failure, set an exception
and return NULL
.
It is legal for a capsule to have a NULL
name. This makes a NULL
return
code somewhat ambiguous; use PyCapsule_IsValid()
or
PyErr_Occurred()
to disambiguate.
PyCapsule_Import
(const char *name, int no_block)Import a pointer to a C object from a capsule attribute in a module. The
name parameter should specify the full name to the attribute, as in
module.attribute
. The name stored in the capsule must match this
string exactly. If no_block is true, import the module without blocking
(using PyImport_ImportModuleNoBlock()
). If no_block is false,
import the module conventionally (using PyImport_ImportModule()
).
Return the capsuleās internal pointer on success. On failure, set an
exception and return NULL
.
PyCapsule_IsValid
(PyObject *capsule, const char *name)Determines whether or not capsule is a valid capsule. A valid capsule is
non-NULL
, passes PyCapsule_CheckExact()
, has a non-NULL
pointer
stored in it, and its internal name matches the name parameter. (See
PyCapsule_GetPointer()
for information on how capsule names are
compared.)
In other words, if PyCapsule_IsValid()
returns a true value, calls to
any of the accessors (any function starting with PyCapsule_Get()
) are
guaranteed to succeed.
Return a nonzero value if the object is valid and matches the name passed in.
Return 0
otherwise. This function will not fail.
PyCapsule_SetContext
(PyObject *capsule, void *context)Set the context pointer inside capsule to context.
Return 0
on success. Return nonzero and set an exception on failure.
PyCapsule_SetDestructor
(PyObject *capsule, PyCapsule_Destructor destructor)Set the destructor inside capsule to destructor.
Return 0
on success. Return nonzero and set an exception on failure.
PyCapsule_SetName
(PyObject *capsule, const char *name)Set the name inside capsule to name. If non-NULL
, the name must
outlive the capsule. If the previous name stored in the capsule was not
NULL
, no attempt is made to free it.
Return 0
on success. Return nonzero and set an exception on failure.
PyCapsule_SetPointer
(PyObject *capsule, void *pointer)Set the void pointer inside capsule to pointer. The pointer may not be
NULL
.
Return 0
on success. Return nonzero and set an exception on failure.