Context Variables Objects ¶

3.7 版添加。

Changed in version 3.7.1:

注意

In Python 3.7.1 the signatures of all context variables C APIs were changed 要使用 PyObject pointers instead of PyContext , PyContextVar ，和 PyContextToken ，如：

// in 3.7.0:
PyContext *PyContext_New(void);
// in 3.7.1+:
PyObject *PyContext_New(void);

见 bpo-34762 了解更多细节。

This section details the public C API for the contextvars 模块。

type PyContext ¶: The C structure used to represent a contextvars.Context 对象。

type PyContextVar ¶: The C structure used to represent a contextvars.ContextVar 对象。

type PyContextToken ¶: The C structure used to represent a contextvars.Token 对象。

PyTypeObject PyContext_Type ¶: The type object representing the context 类型。

PyTypeObject PyContextVar_Type ¶: The type object representing the 上下文变量 类型。

PyTypeObject PyContextToken_Type ¶: The type object representing the context variable token 类型。

Type-check macros:

int PyContext_CheckExact ( PyObject * o ) ¶: 返回 True 若 o 是类型 PyContext_Type . o 不得为 NULL . This function always succeeds.

int PyContextVar_CheckExact ( PyObject * o ) ¶: 返回 True 若 o 是类型 PyContextVar_Type . o 不得为 NULL . This function always succeeds.

int PyContextToken_CheckExact ( PyObject * o ) ¶: 返回 True 若 o 是类型 PyContextToken_Type . o 不得为 NULL . This function always succeeds.

Context object management functions:

PyObject * PyContext_New ( void ) ¶: 返回值：新引用。
Create a new empty context object. Returns NULL if an error has occurred.

PyObject * PyContext_Copy ( PyObject * ctx ) ¶: 返回值：新引用。
Create a shallow copy of the passed ctx context object. Returns NULL if an error has occurred.

PyObject * PyContext_CopyCurrent ( void ) ¶: 返回值：新引用。
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 当出错时。

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 当出错时。

Context variable functions:

PyObject * PyContextVar_New ( const char * 名称 , PyObject * def ) ¶: 返回值：新引用。
创建新的 ContextVar 对象。 name parameter is used for introspection and debug purposes. The def parameter specifies a default value for the context variable, or NULL for no default. If an error has occurred, this function returns NULL .

int PyContextVar_Get ( PyObject * var , PyObject * default_value , PyObject * * 值 ) ¶

Get the value of a context variable. Returns -1 if an error has occurred during lookup, and 0 if no error occurred, whether or not a value was found.

If the context variable was found, value will be a pointer to it. If the context variable was not found, value will point to:

default_value ，若不 NULL ;
the default value of var ，若不 NULL ;
NULL

Except for NULL , the function returns a new reference.

PyObject * PyContextVar_Set ( PyObject * var , PyObject * 值 ) ¶: 返回值：新引用。
Set the value of var to value in the current context. Returns a new token object for this change, or NULL if an error has occurred.

int PyContextVar_Reset ( PyObject * var , PyObject * token ) ¶: Reset the state of the var context variable to that it was in before PyContextVar_Set() that returned the token was called. This function returns 0 on success and -1 当出错时。

Context Variables Objects ¶

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