How to get the return value from a thread using python?

0 votes

How to get the value 'foo' which is returned from the thread as shown below?

from threading import Thread

def foo(bar):
    print 'hello {}'.format(bar)
    return 'foo'

thread = Thread(target=foo, args=('world!',))
thread.start()
ret = thread.join()
print ret

 Returns None in the above case.

Thanks for the help!

Dec 3, 2018 in Python by Anirudh
• 2,070 points

edited Dec 19, 2018 by Anirudh 14,332 views

1 answer to this question.

0 votes

You don't need to change your existing code:

import Queue
from threading import Thread

def foo(bar):
    print 'hello {0}'.format(bar)
    return 'foo'

que = Queue.Queue()

t = Thread(target=lambda q, arg1: q.put(foo(arg1)), args=(que, 'world!'))
t.start()
t.join()
result = que.get()
print result

It can be also easily adjusted to a multi-threaded environment as well. Check this below:

import Queue
from threading import Thread

def foo(bar):
    print 'hello {0}'.format(bar)
    return 'foo'

que = Queue.Queue()
threads_list = list()

t = Thread(target=lambda q, arg1: q.put(foo(arg1)), args=(que, 'world!'))
t.start()
threads_list.append(t)

# Add more threads here
...
threads_list.append(t2)
...
threads_list.append(t3)
...

# Join all the threads
for t in threads_list:
    t.join()

# Check thread's return value
while not que.empty():
    result = que.get()
    print result

Hope this helps, happy learning!

answered Dec 3, 2018 by Nymeria
• 3,520 points

edited Dec 19, 2018 by Nymeria

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