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"""
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
from prompt_toolkit import __version__ as ptk_version
PTK3 = ptk_version.startswith('3.')
# 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):
"""
Inputhook for asyncio event loop integration.
"""
# For prompt_toolkit 3.0, this input hook literally doesn't do anything.
# The event loop integration here is implemented in `interactiveshell.py`
# by running the prompt itself in the current asyncio loop. The main reason
# for this is that nesting asyncio event loops is unreliable.
if PTK3:
return
# For prompt_toolkit 2.0, we can run the current asyncio event loop,
# because prompt_toolkit 2.0 uses a different event loop internally.
def stop():
loop.stop()
fileno = context.fileno()
loop.add_reader(fileno, stop)
try:
loop.run_forever()
finally:
loop.remove_reader(fileno)
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