Return value from function in thread error

Question

I have written a script in which a function calls 2 different functions together using Multi Threading.

def video_image(link_ID): threadp = ThreadPool(processes=1) res = threadp.apply_async(displayImage,( link_ID)) return_val = res.get() tid = Thread(target=publishIAmFree) tid.start() if return_val == True: ............ ............ def displayImage(link_ID): playFlag = True os.system("pkill feh") cmd = "feh /home/fa/Desktop/%s" % (link_ID) os.system(cmd) return playFlag

But, I am getting this error.

 File "C:/Users/user1/PycharmProjects/MediPlayerStructured/venv/Include/main_new_concept.py", line 281, in videoImageFunction video_image(link_ID) File "C:/Users/user1/PycharmProjects/MediPlayerStructured/venv/Include/main_new_concept.py", line 349, in video_image return_val = res.get() File "C:\Users\user1\AppData\Local\Programs\Python\Python37\lib\multiprocessing\pool.py", line 657, in get raise self._value File "C:\Users\user1\AppData\Local\Programs\Python\Python37\lib\multiprocessing\pool.py", line 121, in worker result = (True, func(*args, **kwds)) TypeError: displayImage() takes 1 positional argument but 23 were given

What is this error

TypeError: displayImage() takes 1 positional argument but 23 were given

and how do I solve this?

user2201041 · Accepted Answer · 2018-09-20 14:21:15Z

You're missing a comma. The simple way to reproduce this (in Python2) is

>>> apply(len, ('test')) Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: len() takes exactly one argument (4 given) >>> apply(len, ('test',)) 4

The problem occurs because the args argument is treated as a sequence of arguments. I assume you're passing a string, which is a sequence, so each character becomes a separate argument.

Calling res = threadp.apply_async(displayImage, (link_ID, )) will let Python interpret it as you meant, with link_ID as the first element of a sequence.

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