Using the same thread with different functions in python

Question

I'm new to threading. I wrote this program where I'm trying to execute 2 different functions using threads. I tried to run different functions using the same thread by changing the target and args parameters one after the other :

import threading
import datetime
import Queue

a=Queue.Queue()
b=Queue.Queue()
q=Queue.Queue()

class MyThread(threading.Thread):
    def __init__(self,q):
        threading.Thread.__init__(self)
        self.que=q
        t1=threading.Thread(target=self.prints,args=(4,))
        t2=threading.Thread(target=self.printy,args=(6,self.que,))
        t1.start()
        t2.start()
        item=self.que.get()
        print(item)
        print "*"*30
        it=item*2
        print(it)
        t1.join()

    def main(self):
        t3=threading.Thread(target=self.prints,args=(3,))
        t4=threading.Thread(target=self.printy,args=(5,self.que,))
        t3.start()
        t4.start()
        item=self.que.get()
        print(item)
        print "#"*30
        it=item*2
        print(it)
        t2=threading.Thread(target=self.prints,args=(8,))
        t4=threading.Thread(target=self.prints,args=(7,))
        t2.start()
        t4.start()
        t2.join()
        t3.join()
        t4.join()

    def prints(self,i):
        while(i>0):
            print "i="+str(i)+" "+str(datetime.datetime.now().time())+"\n"
            i=i-1

    def printy(self,i,b):
        r=0
        while(i<10):
            print "i="+str(i)+" "+str(datetime.datetime.now().time())+"\n"
            i=i+1
            r=r+i
        self.que.put(r)

if __name__=='__main__':
    MyThread(a).main()

It executed without throwing any error and also gave me the output I wanted, but I wanted to know if :

This is the right way to do so? Otherwise, What is the right way to run multiple functions using the same thread as a reusable unit?.
In a simple program like this, it seems harmless enough but what about more complex programs with many more functions? Any potential problems that could arise?

enthus1ast · Accepted Answer · 2016-02-25 13:34:18Z

2

from multiprocessing import Pool

def f(x):
    return x*x*x

def b(x):
    return x*x    

if __name__ == '__main__':
    p = Pool(5)
    print(p.map(f, [1, 2, 3]))
    print(p.map(b, [1, 2, 3]))

>> [1, 8, 27]
>> [1, 4, 9]

Please notice that you can't run this example in an ipython session!

edit with threading:

import threading
import queue
q = queue.deque()


def niceFunc1(data):
  return reversed(data)

def niceFunc2(data):
  return "Hey there :%s" % data



q.append( (niceFunc1,"gude") )
q.append( (niceFunc1,"test") )
q.append( (niceFunc2,"test") )
q.append( (niceFunc2,"123") )


def worker():
  for each in q:
    print(each[0](each[1]))


t=threading.Thread(target=worker)
t.start()

t2=threading.Thread(target=worker)
t2.start()

edited Feb 25, 2016 at 13:34

answered Feb 25, 2016 at 13:05

enthus1ast

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4 Comments

skrowten_hermit Over a year ago

So, this can be done only using multiprocessing class and not threading class? I wanted to know if there is a safe way of doing this using threading.

enthus1ast Over a year ago

You could have a queue where the thread is pulling a (function,data) tuple. Then you could execute the function with the provided data.

skrowten_hermit Over a year ago

Could you throw some more light on the same with an example please?

enthus1ast Over a year ago

please see my edit. I've not created the class but you should get the idea.

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