上下文变量对象

注解

在 3.7.1 版更改:

在 Python 3.7.1 中，所有上下文变量 C API 的签名被 更改 为使用 PyObject 指针而不是 PyContext, PyContextVar 以及 PyContextToken，例如:

// in 3.7.0:
PyContext *PyContext_New(void);

// in 3.7.1+:
PyObject *PyContext_New(void);

详情请参阅:issue: ' 34762 '。

3.7 新版功能.

This section details the public C API for the contextvars module.

PyContext

The C structure used to represent a contextvars.Context object.

PyContextVar

The C structure used to represent a contextvars.ContextVar object.

PyContextToken

The C structure used to represent a contextvars.Token object.

PyTypeObject PyContext_Type

The type object representing the context type.

PyTypeObject PyContextVar_Type

The type object representing the context variable type.

PyTypeObject PyContextToken_Type

The type object representing the context variable token type.

类型检查宏：

int PyContext_CheckExact(PyObject *o)

Return true if o is of type PyContext_Type. o must not be NULL. This function always succeeds.

int PyContextVar_CheckExact(PyObject *o)

Return true if o is of type PyContextVar_Type. o must not be NULL. This function always succeeds.

int PyContextToken_CheckExact(PyObject *o)

Return true if o is of type PyContextToken_Type. o must not be NULL. This function always succeeds.

Context object management functions:

PyObject *PyContext_New(void)

Return value: New reference.

Create a new empty context object. Returns NULL if an error has occurred.

PyObject *PyContext_Copy(PyObject *ctx)

Return value: New reference.

Create a shallow copy of the passed ctx context object. Returns NULL if an error has occurred.

PyObject *PyContext_CopyCurrent(void)

Return value: New reference.

Create a shallow copy of the current thread context. Returns NULL if an error has occurred.

int PyContext_Enter(PyObject *ctx)

Set ctx as the current context for the current thread. Returns 0 on success, and -1 on error.

int PyContext_Exit(PyObject *ctx)

Deactivate the ctx context and restore the previous context as the current context for the current thread. Returns 0 on success, and -1 on error.

int PyContext_ClearFreeList()

Clear the context variable free list. Return the total number of freed items. This function always succeeds.

Context variable functions:

PyObject *PyContextVar_New(const char *name, PyObject *def)

Return value: New reference.

创建一个新的' ' ContextVar' '对象。形参*name*用于自我检查和调试目的。可选形参*def*为上下文变量指定默认值。如果发生错误，这个函数返回' ' NULL ' '。

int PyContextVar_Get(PyObject *var, PyObject *default_value, PyObject **value)

获取上下文变量的值。如果在查找过程中发生错误，返回' ' -1 ' '，如果没有发生错误，无论是否找到值，都返回' ' 0 ' '，

如果找到上下文变量，value 将是指向它的指针。 如果上下文变量 没有 找到，value 将指向：

• default_value，如果非``NULL``;

• var 的默认值，如果不是 NULL；

• NULL

如果找到该值，函数将创建对它的新引用。

PyObject *PyContextVar_Set(PyObject *var, PyObject *value)

Return value: New reference.

在当前上下文中将 var 的值设为 value。 返回指向 PyObject 对象的指针，如果发生错误则返回 NULL。

int PyContextVar_Reset(PyObject *var, PyObject *token)

将上下文变量 var 的状态重置为它在返回 token 的 PyContextVar_Set() 被调用之前的状态。 此函数成功时返回 0，出错时返回 -1。