Python3 multi threading

Question

I am working on a Youtube downloader script and met difficulty in multi->threading . I put the urls needs to be downloaded in a queue and get them one by >one with new thread spawning. Below is my code and the error are within the commant. >Please advise.

from queue import Queue


#put all the urls in 'q'
q = Queue()
with open(r'c:\ProgramData\youtube_download\122.txt', 'r') as f : 
    for url in f.readlines():
        url = url.strip()
        q.put(url)  #totally 18 urls are stored in the queue


def My_download( url_d):

    yt = YouTube(url_d)
    video = yt.get('mp4', '720p')
    video.download(r'C:/Users/abc/Desktop')  # The default video directory

def main():

    while  not q.empty():
        url_d = q.get()
        q.task_done()
##    print(str(q.qsize()) + url_d)  >>until this step, everything works as expected

        t = Thread(target = My_download, args = url_d)  #>>TypeError: My_download() takes 1 positional argument but 92 were given
        t.start()

    q.join()


if __name__ == "__main__":

    main()

Answer 1

Change to

t = Thread(target = My_download, args = (url_d,))  

From the docs

args is the argument tuple for the target invocation. Defaults to ().

When you send pass a string instead of tuple, it unpacks the string to a tuple of n elements(92 in your case, and so the error)

Answer 2

In

Thread(target = My_download, args = url_d)

args is the argument sequence for the invocation of target. The arguments are unpacked when calling My_download. For example,

Thread(target = My_download, args = [1, 2, 3])

would try to call My_download(1, 2, 3) eventually. This triggers the the TypeError because your function takes exactly one argument. To prevent the unpacking, you can wrap args in another sequence of length one, e.g.

Thread(target = My_download, args = [url_d])

or modify My_download such that it accepts an arbitrary number of arguments by using the *args syntax.