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+.. highlightlang:: c
+
+.. _capsules:
+
+Capsules
+--------
+
+.. index:: object: Capsule
+
+Refer to :ref:`using-capsules` for more information on using these objects.
+
+
+.. ctype:: PyCapsule
+
+   This subtype of :ctype:`PyObject` represents an opaque value, useful for C
+   extension modules who need to pass an opaque value (as a :ctype:`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.
+
+.. ctype:: PyCapsule_Destructor
+
+   The type of a destructor callback for a capsule.  Defined as::
+
+      typedef void (*PyCapsule_Destructor)(PyObject *);
+
+   See :cfunc:`PyCapsule_New` for the semantics of PyCapsule_Destructor
+   callbacks.
+
+
+.. cfunction:: int PyCapsule_CheckExact(PyObject *p)
+
+   Return true if its argument is a :ctype:`PyCapsule`.
+
+
+.. cfunction:: PyObject* PyCapsule_New(void *pointer, const char *name, PyCapsule_Destructor destructor)
+
+   Create a :ctype:`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 :cfunc:`PyCapsule_Import`.
+
+
+.. cfunction:: void* 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 :cfunc:`strcmp` to compare capsule
+   names.
+
+
+.. cfunction:: PyCapsule_Destructor 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 :cfunc:`PyCapsule_IsValid` or
+   :cfunc:`PyErr_Occurred` to disambiguate.
+
+
+.. cfunction:: void* 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 :cfunc:`PyCapsule_IsValid` or
+   :cfunc:`PyErr_Occurred` to disambiguate.
+
+
+.. cfunction:: const char* 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 :cfunc:`PyCapsule_IsValid` or
+   :cfunc:`PyErr_Occurred` to disambiguate.
+
+
+.. cfunction:: void* 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 :cfunc:`PyImport_ImportModuleNoBlock`).  If *no_block* is false,
+   import the module conventionally (using :cfunc:`PyImport_ImportModule`).
+
+   Return the capsule's internal *pointer* on success.  On failure, set an
+   exception and return *NULL*.  However, if :cfunc:`PyCapsule_Import` failed to
+   import the module, and *no_block* was true, no exception is set.
+
+.. cfunction:: int PyCapsule_IsValid(PyObject *capsule, const char *name)
+
+   Determines whether or not *capsule* is a valid capsule.  A valid capsule is
+   non-*NULL*, passes :cfunc:`PyCapsule_CheckExact`, has a non-*NULL* pointer
+   stored in it, and its internal name matches the *name* parameter.  (See
+   :cfunc:`PyCapsule_GetPointer` for information on how capsule names are
+   compared.)
+
+   In other words, if :cfunc:`PyCapsule_IsValid` returns a true value, calls to
+   any of the accessors (any function starting with :cfunc:`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.
+
+.. cfunction:: int 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.
+
+.. cfunction:: int 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.
+
+.. cfunction:: int 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.
+
+.. cfunction:: int 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.