How to pass parameters to a running python thread

Question

I have a class A extended from threading.Thread, now I want to pass the parameters into the running thread , I can get the thread I wanted by the following script:

find_thread = None
for thread in enumerate():
    if thread.isAlive():
        name = thread.name.split(',')[-1]
        if name == player_id:
            find_thread = thread #inject the parameter into this thread
            break

Where find_thread is an instance of threading.Thread and I have a queue in find_thread.

class A(threading.Thread):
    def __init__(self,queue):
        threading.Thread.__init__(self)
        self.queue =queue
    def run():
        if not self.queue.empty(): #when it's running,I want to pass the parameters here
            a=queue.get()
            process(a) #do something

Is it possible to do this and how?

Well you're already familiar with queue and have a queue.get (recommend get_nowait() instead). So why not just use queue.put_nowait() from whatever thread you want to and have A leverage the queue.get() you have? — pstatix
– pstatix, Commented Sep 11, 2017 at 11:58

GIZ · Accepted Answer · 2017-09-15 08:20:13Z

2

Everything seems fine with your code, you just need to slighty modify it. You've already used threading.Queue I believe , you also used the queue's get method so I wonder why you weren't able to use its put method:

for thread in enumerate():
    if thread.isAlive():
        name = thread.name.split(',')[-1]
        if name == player_id:
            find_thread = thread
            find_thread.queue.put(...)  # put something here
            break

class A(threading.Thread):
    def __init__(self,queue):
        threading.Thread.__init__(self, queue)
        self.queue = queue
    def run():
        a = queue.get()                 # blocks when empty
        process(a)

queue = Queue()
thread1 = A(queue=queue,...)

I removed the check for the empty queue, queue.get blocks when the queue is empty making the check gratuitous here, this is because a is needed by your thread for processing.

edited Sep 15, 2017 at 8:20

answered Sep 11, 2017 at 13:01

GIZ

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1 Comment

Ernie Sender Over a year ago

i think there is a typo, in line " threading.Thread.__init__(self, queue)", you don't need to pass the queue to the init, this will raise an error

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