Python asyncio

最近在看 ayncio 这块内容
于是打算从 asyncio.run 这个 函数作为入口看下内部是如何工作的
下面是源码以及一些分析

如有问题, 欢迎交流

另外 有没得大佬晓得 博客园的 markdown 怎么显示行号啊

def run(main, *, debug=False):

    if events._get_running_loop() is not None:  # 获取当前是否含有 loop
        raise RuntimeError(
            "asyncio.run() cannot be called from a running event loop")

    if not coroutines.iscoroutine(main): #  判断是否是一个 coroutine
        raise ValueError("a coroutine was expected, got {!r}".format(main))

    loop = events.new_event_loop()  # 获取一个 loop

    """
    下面是获取一个 loop 的逻辑
    """
    # get_event_loop_policy().new_event_loop()
    # 其中 get_event_loop_policy 是获取 loop_policy
    # 在 linux 下 默认是使用 _UnixDefaultEventLoopPolicy # asyncio.unix_events._UnixDefaultEventLoopPolicy
    # loop 为 _UnixSelectorEventLoop 的一个实例 # asyncio.unix_events._UnixSelectorEventLoop
    """
    获取 loop end 
    """

    try:
        events.set_event_loop(loop)  # get_event_loop_policy().set_event_loop(loop)
        """
        get_event_loop_policy() -> _UnixDefaultEventLoopPolicy 一个实例
        set_event_loop()  # asyncio.events.BaseDefaultEventLoopPolicy#set_event_loop 
        给 loop_policy 设置 loop 
        放在 loop_policy 的 ThreadLocal 中 (引用变量)
        ps. 最近被引用变量坑的不行...有点怕(弱引用)
        """

        loop.set_debug(debug)
        """
        # todo 暂时不处理
        """
        return loop.run_until_complete(main)
        """
        asyncio.base_events.BaseEventLoop#run_until_complete
        """
        
        """以下是 run_until_complete 的逻辑"""

        def run_until_complete(self, future):

            self._check_closed() # 暂时不管

            new_task = not futures.isfuture(future) # 判断是否是 future toto  task???
            # todo asyncio.ensure_future asyncio.create_task 两者的差别
            future = tasks.ensure_future(future, loop=self)  # create task
            """
            asyncio.tasks.ensure_future
            看了下如果 future 是一个 coroutine 则会调用 create_task
            asyncio.base_events.BaseEventLoop#create_task
            # todo task 内容暂时不看


            future 是 _asyncio.Task 或者是 _asyncio.Future -----asyncio.futures.Future(划掉)
            Task 为 Future 的一个子类
            """

            if new_task:
                # An exception is raised if the future didn't complete, so there
                # is no need to log the "destroy pending task" message
                future._log_destroy_pending = False

            future.add_done_callback(_run_until_complete_cb)
            """
            add_done_callback 是写在 so 文件中了 我并不知道他干了点啥 ~~~~(>_<)~~~~


            可能类似这个吧:
            def add_done_callback(self, fn, *, context=None):
                '''Add a callback to be run when the future becomes done.

                The callback is called with a single argument - the future object. If
                the future is already done when this is called, the callback is
                scheduled with call_soon.
                '''
                if self._state != _PENDING:
                    self._loop.call_soon(fn, self, context=context)
                else:
                    if context is None:
                        context = contextvars.copy_context()
            """

            # todo 有时间再看
            try:
                self.run_forever()
            except:
                if new_task and future.done() and not future.cancelled():
                    # The coroutine raised a BaseException. Consume the exception
                    # to not log a warning, the caller doesn't have access to the
                    # local task.
                    future.exception()
                raise
            finally:
                future.remove_done_callback(_run_until_complete_cb)
            if not future.done():
                raise RuntimeError('Event loop stopped before Future completed.')

            return future.result()
        """-------- run_until_complete ---------   end"""

    finally:
        try:
            _cancel_all_tasks(loop)
            loop.run_until_complete(loop.shutdown_asyncgens())
        finally:
            events.set_event_loop(None)
            loop.close()