Extending
The main direction for asyncio extending is writing custom event loop classes. Asyncio has helpers that could be used to simplify this task.
备注
Third-parties should reuse existing asyncio code with caution, a new Python version is free to break backward compatibility in internal part of API.
Writing a Custom Event Loop
asyncio.AbstractEventLoop declares very many methods. Implementing all them from scratch is a tedious job.
A loop can get many common methods implementation for free by inheriting from asyncio.BaseEventLoop
.
In turn, the successor should implement a bunch of private methods declared but not implemented in asyncio.BaseEventLoop
.
For example, loop.create_connection()
checks arguments, resolves DNS addresses, and calls loop._make_socket_transport()
that should be implemented by inherited class. The _make_socket_transport()
method is not documented and is considered as an internal API.
Future and Task private constructors
asyncio.Future and asyncio.Task should be never created directly, please use corresponding loop.create_future() and loop.create_task(), or asyncio.create_task() factories instead.
However, third-party event loops may reuse built-in future and task implementations for the sake of getting a complex and highly optimized code for free.
For this purpose the following, private constructors are listed:
Future.__init__(**, loop=None*)
Create a built-in future instance.
loop is an optional event loop instance.
Task.__init__(coro, **, loop=None, name=None, context=None*)
Create a built-in task instance.
loop is an optional event loop instance. The rest of arguments are described in loop.create_task() description.
在 3.11 版更改: context argument is added.
Task lifetime support
A third party task implementation should call the following functions to keep a task visible by asyncio.get_tasks()
and asyncio.current_task():
asyncio._register_task(task)
Register a new task as managed by asyncio.
Call the function from a task constructor.
asyncio._unregister_task(task)
Unregister a task from asyncio internal structures.
The function should be called when a task is about to finish.
asyncio._enter_task(loop, task)
Switch the current task to the task argument.
Call the function just before executing a portion of embedded coroutine (coroutine.send() or coroutine.throw()).
asyncio._leave_task(loop, task)
Switch the current task back from task to None
.
Call the function just after coroutine.send() or coroutine.throw() execution.