###### tags: `python` `threading`

# Threading

## solve problems
>[file name ≠ threading](https://stackoverflow.com/questions/41012121/attributeerror-module-object-has-no-attribute-rlock)

## Added a job

import threading

def threadJob():
    
    print("this job displays current thread, number is %s" %threading.currentThread())

def main():
    addedThread=threading.Thread(target=threadJob)
    addedThread.start()

    
    # to tell us how many threading
    print(threading.activeCount())
    # to tell us threading name   
    print(threading.enumerate())  #enumerate 列舉
    # to tell us currently execute threads 
    print(threading.currentThread())
    
if __name__ == '__main__':

    main()

## join()

to control threading executed sequence

import threading
import time


def thread1():
    print("T1 start\n")
    for i in [3,2,1]:
        print(i)
        time.sleep(1)
    print("T1 all down\n")

def thread2():
    print("T2 start\n")
    for i in [5,4,3,2,1]:
        print(i)
        time.sleep(1)
    print("T2 all down\n")

def main():
    addedThread1=threading.Thread(target=thread1,name="T1")
    addedThread2=threading.Thread(target=thread2,name="T2")
    addedThread1.start()
    addedThread2.start()



    addedThread1.join() # join, it will wait for the subthread to execute completely and it will execute follow programs
    addedThread2.join()

    print("main finished\n")
   






if __name__ == '__main__':
    main()

>join()
It will wait for the subthread to execute completely and it will execute follow programs

## mult-threading computing

import threading
from queue import Queue
import time


list =[[1,2,3,4],[4,5,6,7],[8,9,10,11],[12,12,12,12]]

def job(list,q):
    for i in range(len(list)):
        list[i] = list[i]**2
        time.sleep(1)
        print(f'through compute time is {i}')
    q.put(list)


def multithreading():
    q=Queue()
    threads=[]

    for i in range(4):
        thread=threading.Thread(target=job,args=(list[i],q))
        thread.start()
        threads.append(thread)

    for thread in threads:
        threads =thread.join()

    result=[]
    for i in range(4):
        result.append(q.get())
    

    print(result)
    print("We didn't wait 12 seconds to complete computing if we use multi-threding to compute")
if __name__ =="__main__":
    multithreading()

>Remark:
>In multi-threading didn't return values
>So, we use Queue instead of the return