Context Variables Objects¶
Added in version 3.7.
Changed in version 3.7.1:
Note
In Python 3.7.1 the signatures of all context variables
C APIs were changed to use PyObject pointers instead
of PyContext, PyContextVar, and
PyContextToken, e.g.:
// in 3.7.0:
PyContext *PyContext_New(void);
// in 3.7.1+:
PyObject *PyContext_New(void);
See bpo-34762 for more details.
This section details the public C API for the contextvars module.
- 
type PyContext¶
- The C structure used to represent a - contextvars.Contextobject.
- 
type PyContextVar¶
- The C structure used to represent a - contextvars.ContextVarobject.
- 
type PyContextToken¶
- The C structure used to represent a - contextvars.Tokenobject.
- 
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. 
Type-check macros:
- 
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 NULLif an error has occurred.
- 
PyObject *PyContext_Copy(PyObject *ctx)¶
- Return value: New reference.Create a shallow copy of the passed ctx context object. Returns NULLif an error has occurred.
- 
PyObject *PyContext_CopyCurrent(void)¶
- Return value: New reference.Create a shallow copy of the current thread context. Returns NULLif an error has occurred.
- 
int PyContext_Enter(PyObject *ctx)¶
- Set ctx as the current context for the current thread. Returns - 0on success, and- -1on error.
- 
int PyContext_Exit(PyObject *ctx)¶
- Deactivate the ctx context and restore the previous context as the current context for the current thread. Returns - 0on success, and- -1on error.
Context variable functions:
- 
PyObject *PyContextVar_New(const char *name, PyObject *def)¶
- Return value: New reference.Create a new ContextVarobject. The name parameter is used for introspection and debug purposes. The def parameter specifies a default value for the context variable, orNULLfor no default. If an error has occurred, this function returnsNULL.
- 
int PyContextVar_Get(PyObject *var, PyObject *default_value, PyObject **value)¶
- Get the value of a context variable. Returns - -1if an error has occurred during lookup, and- 0if 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, if not - NULL;
- the default value of var, if not - NULL;
- NULL
 - Except for - NULL, the function returns a new reference.
- 
PyObject *PyContextVar_Set(PyObject *var, PyObject *value)¶
- Return value: New reference.Set the value of var to value in the current context. Returns a new token object for this change, or NULLif 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- 0on success and- -1on error.