Input hooks

Input hooks are a tool for inserting an external event loop into the prompt_toolkit event loop, so that the other loop can run as long as prompt_toolkit (actually asyncio) is idle. This is used in applications like IPython, so that GUI toolkits can display their windows while we wait at the prompt for user input.

As a consequence, we will “trampoline” back and forth between two event loops.


This will use a SelectorEventLoop, not the :class: ProactorEventLoop (on Windows) due to the way the implementation works (contributions are welcome to make that work).

from prompt_toolkit.eventloop.inputhook import set_eventloop_with_inputhook

def inputhook(inputhook_context):
    # At this point, we run the other loop. This loop is supposed to run
    # until either `inputhook_context.fileno` becomes ready for reading or
    # `inputhook_context.input_is_ready()` returns True.

    # A good way is to register this file descriptor in this other event
    # loop with a callback that stops this loop when this FD becomes ready.
    # There is no need to actually read anything from the FD.

    while True:


# Any asyncio code at this point will now use this new loop, with input
# hook installed.