Python Threading module Error argument after * must be an iterable, not int

Question

So I was playing around with the threading module in order to understand the basics of it and when I ran my code, I get an error that does not clearly specify what did I do wrong. here is the code, and bellow that, you can find the error log:

import threading
import time

start = time.perf_counter()


def square(y):
    print('Starting processing')
    for x in range(y):
        i = x * x
    print(f'Done processing {i}')

threads = []

# creating thread
for _ in range(10):
    thread = threading.Thread(target=square, args=1000000)
    # starting thread
    thread.start()
    threads.append(thread)

# makes sure that the threads complete before moving to the rest of the code
for i in threads:
    i.join()




finish = time.perf_counter()

print(f'Done processing in {round(finish - start, 4)} second(s).')

And I get this error:

Exception in thread Thread-1:
Traceback (most recent call last):
    File "C:\Users\EM\AppData\Local\Programs\Python\Python37\lib\threading.py", line 917, in 
    _bootstrap_innerself.run()
    File "C:\Users\EM\AppData\Local\Programs\Python\Python37\lib\threading.py", line 865, in 
    runself._target(*self._args, **self._kwargs)
TypeError: square() argument after * must be an iterable, not int

Exception in thread Thread-3:
Traceback (most recent call last):
    File "C:\Users\EM\AppData\Local\Programs\Python\Python37\lib\threading.py", line 917, 
    in_bootstrap_innerself.run()
    File "C:\Users\EM\AppData\Local\Programs\Python\Python37\lib\threading.py", line 865, in 
    runself._target(*self._args, **self._kwargs)
TypeError: square() argument after * must be an iterable, not int

Exception in thread Thread-4:
Traceback (most recent call last):
    File "C:\Users\EM\AppData\Local\Programs\Python\Python37\lib\threading.py", line 917, in 
    _bootstrap_inner
self.run()
    File "C:\Users\EM\AppData\Local\Programs\Python\Python37\lib\threading.py", line 865, in 
    runself._target(*self._args, **self._kwargs)
TypeError: square() argument after * must be an iterable, not int

Exception in thread Thread-2:
Traceback (most recent call last):
    File "C:\Users\EM\AppData\Local\Programs\Python\Python37\lib\threading.py", line 917, in 
    _bootstrap_innerself.run()
    File "C:\Users\EM\AppData\Local\Programs\Python\Python37\lib\threading.py", line 865, in run
    self._target(*self._args, **self._kwargs)
TypeError: square() argument after * must be an iterable, not int
Exception in thread Thread-5:
Traceback (most recent call last):
    File "C:\Users\EM\AppData\Local\Programs\Python\Python37\lib\threading.py", line 917, in 
    _bootstrap_innerself.run()
    File "C:\Users\EM\AppData\Local\Programs\Python\Python37\lib\threading.py", line 865, in run 
    self._target(*self._args, **self._kwargs)
TypeError: square() argument after * must be an iterable, not int


Exception in thread Thread-6:
Traceback (most recent call last):
    File "C:\Users\EM\AppData\Local\Programs\Python\Python37\lib\threading.py", line 917, in 
    _bootstrap_innerself.run()
    File "C:\Users\EM\AppData\Local\Programs\Python\Python37\lib\threading.py", line 865, in run
    self._target(*self._args, **self._kwargs)
TypeError: square() argument after * must be an iterable, not int

Exception in thread Thread-7:
Traceback (most recent call last):
    File "C:\Users\EM\AppData\Local\Programs\Python\Python37\lib\threading.py", line 917, in 
    _bootstrap_innerself.run()
    File "C:\Users\EM\AppData\Local\Programs\Python\Python37\lib\threading.py", line 865, in run
    self._target(*self._args, **self._kwargs)
TypeError: square() argument after * must be an iterable, not int

Exception in thread Thread-8:
Traceback (most recent call last):
    File "C:\Users\EM\AppData\Local\Programs\Python\Python37\lib\threading.py", line 917, in 
    _bootstrap_innerself.run()
    File "C:\Users\EM\AppData\Local\Programs\Python\Python37\lib\threading.py", line 865, in run
    self._target(*self._args, **self._kwargs)
TypeError: square() argument after * must be an iterable, not int

Exception in thread Thread-9:
Traceback (most recent call last):
    File "C:\Users\EM\AppData\Local\Programs\Python\Python37\lib\threading.py", line 917, in 
    _bootstrap_innerself.run()
    File "C:\Users\EM\AppData\Local\Programs\Python\Python37\lib\threading.py", line 865, in run
    self._target(*self._args, **self._kwargs)
TypeError: square() argument after * must be an iterable, not int

Exception in thread Thread-10:
Traceback (most recent call last):
    File "C:\Users\EM\AppData\Local\Programs\Python\Python37\lib\threading.py", line 917, in 
    _bootstrap_innerself.run()
    File "C:\Users\EM\AppData\Local\Programs\Python\Python37\lib\threading.py", line 865, in run
    self._target(*self._args, **self._kwargs)
TypeError: square() argument after * must be an iterable, not int

I do not know what is wrong with my code, and the error log does not indicate where did the error stem from.

Your args= parameter needs to be iterable. I suggest a tuple: Thread(target=square, args=(1000000,)) — quamrana
– quamrana, Commented Jun 8, 2020 at 9:28

Vanillaboy · Accepted Answer · 2020-06-08 09:29:16Z

15

Try

thread = threading.Thread(target=square, args=(1000000,))

The function is expecting an tuple / list argument, which is iterable, so if you have more arguments to pass, you just do it like this args=(param1, param2, param3).

answered Jun 8, 2020 at 9:29

Vanillaboy

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1 Comment

Mehdi Rezzag Hebla Over a year ago

Thank you, that was it.

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