# 胶囊

有关使用这些对象的更多信息请参阅 给扩展模块提供C API。

3.1 新版功能.

`PyCapsule`

  这个 `PyObject` 的子类型代表着一个任意值，当需要通过 Python 代码将任意值（以 `void*` 指针的形式）从 C 扩展模块传递给其他 C 代码时非常有用。它通常用于将指向一个模块中定义的 C 语言函数指针传递给其他模块，以便可以从那里调用它们。这允许通过正常的模块导入机制访问动态加载的模块中的 C API。

`PyCapsule_Destructor`

  这种类型的一个析构器返回一个胶囊，定义如下：

      typedef void (*PyCapsule_Destructor)(PyObject *);

  参阅 `PyCapsule_New()` 来获取 PyCapsule_Destructor 返回值的语义。

int `PyCapsule_CheckExact`(PyObject *p)

  如果参数是一个 `PyCapsule` 则返回 True

PyObject* `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()`.

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 `strcmp()` to compare capsule names.

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 `PyCapsule_IsValid()` or `PyErr_Occurred()` to disambiguate.

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 `PyCapsule_IsValid()` or `PyErr_Occurred()` to disambiguate.

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 `PyCapsule_IsValid()` or `PyErr_Occurred()` to disambiguate.

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 `PyImport_ImportModuleNoBlock()`). If no_block is false, import the module conventionally (using `PyImport_ImportModule()`).

  Return the capsule’s internal pointer on success. On failure, set an exception and return NULL.

int `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.

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.

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.

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.

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.