Python threading error - must be an iterable, not int

Question

I'm trying to calculate rolling r-squared of regression among first column and other columns in a dataframe (first column and second, first column and third etc.) But when I try threading, it kept telling me the error that

TypeError: ParallelRegression() argument after * must be an iterable, not int".

I'm wondering how do I fix this? Thanks very much!

import threading

totalThreads=3 #three different colors
def ParallelRegression(threadnum):
    for i in range(threadnum):
        res[:,i]=sm.OLS(df.iloc[:,0], df.iloc[:,i+1]).fit().rsquared
threads=[]
for threadnum in range(totalThreads):
    t=threading.Thread(target=ParallelRegression,args=(threadnum))
    threads.append(t)
    t.start()
for threadnum in range(totalThreads):
    threads[threadnum].join()

See a summary of the data (df) in the picture linked below:

Answer 1

threading.Thread class needs an iterable of arguments as the args parameter. You're passing args=(threadnum) which is a single int object, you need to pass some iterable object that would allow multiple args, even when you only want to pass one arg.

args=[threadnum] would work, because that makes a list which is iterable.

Answer 2

There is another solution: add a comma at the end of "threadnum"

t=threading.Thread(target=ParallelRegression,args=(threadnum,))