Add asyncio input hook for event loop integration.

IPython/terminal/pt_inputhooks/asyncio.py

@@ -0,0 +1,43 b''
+"""
+Inputhook for running the original asyncio event loop while we're waiting for
+input.
+
+By default, in IPython, we run the prompt with a different asyncio event loop,
+because otherwise we risk that people are freezing the prompt by scheduling bad
+coroutines. E.g., a coroutine that does a while/true and never yield back
+control to the loop. We can't cancel that.
+
+However, sometimes we want the asyncio loop to keep running while waiting for
+a prompt.
+
+The following example will print the numbers from 1 to 10 above the prompt,
+while we are waiting for input. (This works also because we use
+prompt_toolkit`s `patch_stdout`)::
+
+    In [1]: import asyncio
+
+    In [2]: %gui asyncio
+
+    In [3]: async def f():
+       ...:     for i in range(10):
+       ...:         await asyncio.sleep(1)
+       ...:         print(i)
+
+
+    In [4]: asyncio.ensure_future(f())
+
+"""
+import asyncio
+
+# Keep reference to the original asyncio loop, because getting the event loop
+# within the input hook would return the other loop.
+loop = asyncio.get_event_loop()
+
+
+def inputhook(context):
+    def stop():
+        loop.stop()
+
+    loop.add_reader(context.fileno(), stop)
+    context.fileno()
+    loop.run_forever()

IPython/terminal/pt_inputhooks/__init__.py

@@ -12,7 +12,8 b' backends = ['
     'tk',
     'wx',
     'pyglet', 'glut',
-    'osx'
+    'osx',
+    'asyncio'
 ]
 
 registered = {}