asyncio tkinter

tkasync.py

"""
Sample file to enable tkinter to run with co-routine and asyncio code
with no need for extra threads or blocking the UI


(this will likely be upgraded to a full package at some point in time)

"""


import asyncio, sys, tkinter
from functools import wraps
import inspect


_tkasync_tasks = set()

def tkasync(func):
    """Decorator to enable asyncio callbacks for tkinter
    """
    if not inspect.iscoroutinefunction(func):
        return func # nothing to be done

    @wraps(func)
    def wrapper(*args, **kwargs):
        coro = func(*args, **kwargs)
        try:
            loop = asyncio.get_running_loop()
        except RuntimeError:
            # no running event loop: we are running in sync context:
            # just create a loop, await for the wrapped function and be done with it
            asyncio.run(coro)
            return

        task = loop.create_task(coro)
        _tkasync_tasks.add(task)

    return wrapper


async def main_async(root):
    """Tkinter async driver, meant to replace tkinter.mainloop
    """
    global _tkasync_tasks
    while True:
        try:
            root.update()
        except Exception as error:
            # FIXME: suppress error message when tkinter app is destroyed.
            print(error, file=sys.stderr)
            raise
        if _tkasync_tasks:
            complete, pending = await asyncio.wait(_tkasync_tasks, timeout=0.005)
            del complete
            _tkasync_tasks = pending
        else:
            await asyncio.sleep(0.005)

############################################################
# Example code just to show something running in parallel


index = 0
interval=250
area = button = root = None


def build():
    global root, area, button
    root = tkinter.Tk()
    button = b = tkinter.Button(root, text="ok", command=click)
    area =l = tkinter.Label(root, text=" " * 80, background="yellow")

    b.pack()
    area.pack()
    root.after(interval, update_color)
    return root


def update_color():
    global index
    colors = "yellow", "red", "blue", "black", "green"
    index += 1
    index %= len(colors)
    area["background"] = colors[index]
    root.after(interval, update_color)

#####################################################
# Example coroutine used as a tkinter callback:
@tkasync
async def click():
    state = button["state"]
    button["state"] = "disabled"
    print("click enter")
    await asyncio.sleep(2)
    print("click exit")
    button["state"] = state if state != "disabled" else "normal"

##########################################
# sample main function
def main():
    root = build()
    # Call this instead of tkinter.mainloop: 
    loop = asyncio.run(main_async(root))

if __name__ == "__main__":
    main()

At line 64 there is an unpack error on area, button, root = None, shouldn't it be something like area = button = root = None?

Yes. Fixed now, thanks.