bpo-32314: Implement asyncio.run() (#4852)

Lib/asyncio/runners.py

@@ -0,0 +1,48 @@
+__all__ = 'run',
+
+from . import coroutines
+from . import events
+
+
+def run(main, *, debug=False):
+    """Run a coroutine.
+
+    This function runs the passed coroutine, taking care of
+    managing the asyncio event loop and finalizing asynchronous
+    generators.
+
+    This function cannot be called when another asyncio event loop is
+    running in the same thread.
+
+    If debug is True, the event loop will be run in debug mode.
+
+    This function always creates a new event loop and closes it at the end.
+    It should be used as a main entry point for asyncio programs, and should
+    ideally only be called once.
+
+    Example:
+
+        async def main():
+            await asyncio.sleep(1)
+            print('hello')
+
+        asyncio.run(main())
+    """
+    if events._get_running_loop() is not None:
+        raise RuntimeError(
+            "asyncio.run() cannot be called from a running event loop")
+
+    if not coroutines.iscoroutine(main):
+        raise ValueError("a coroutine was expected, got {!r}".format(main))
+
+    loop = events.new_event_loop()
+    try:
+        events.set_event_loop(loop)
+        loop.set_debug(debug)
+        return loop.run_until_complete(main)
+    finally:
+        try:
+            loop.run_until_complete(loop.shutdown_asyncgens())
+        finally:
+            events.set_event_loop(None)
+            loop.close()