Simple way to run multiple python threads

Question

I'm importing multiple python threads from different directories and then want to run them simultaneously.

Here's my parent:

import sys
import thread

sys.path.append('/python/loanrates/test')

import test2

thread.start_new_thread(test2.main())

and here's one of my child's:

import json 

def main():

    data = 'ello world'

    print data 

    with open( 'D:/python/loanrates/test/it_worked.json', 'w') as f:
        json.dump(data, f)

if __name__ == '__main__':
    main()

but I am getting this error:

TypeError: start_new_thread expected at least 2 arguments, got 1

What is a simple way I can get this thread started (and then sequentially run multiple threads using the same method)

David if my answer has solved your question please consider accepting it — Idos
– Idos, Commented Feb 22, 2016 at 14:47

Community · Accepted Answer · 2017-05-23 11:59:26Z

1

You also need to provide a tuple with the argument to run the function with. If you have none, pass an empty tuple.

thread.start_new_thread(test2.main, ())

From the docs of thread.start_new_thread(function, args[, kwargs]) (boldface mine):

Start a new thread and return its identifier. The thread executes the function function with the argument list args (which must be a tuple). The optional kwargs argument specifies a dictionary of keyword arguments. When the function returns, the thread silently exits. When the function terminates with an unhandled exception, a stack trace is printed and then the thread exits (but other threads continue to run).

You can also:

thread = Thread(target = test2.main, args, kwargs)

thread.start() // starts the thread

thread.join() // wait

Read more on this approach to creating and working with threads here.

edited May 23, 2017 at 11:59

CommunityBot

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answered Feb 21, 2016 at 11:20

Idos

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8 Comments

David Hancock Over a year ago

I get invalid syntax from using this: thread.start_new_thread(test2.main, ( , ) )

David Hancock Over a year ago

Also using thread = Thread(target = test2.main, args, kwargs) i get Thread is not defined

Idos Over a year ago

"Thread is not defined" -> import the library (stackoverflow.com/questions/28873479/…). I am checking regarding the syntax error now

Idos Over a year ago

Check it now (removed the comma , )

David Hancock Over a year ago

Thanks, however Is still get this error Unhandled exception in thread started by sys.excepthook is missing lost sys.stderr

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