How to prevent tqdm from printing progress bar in newline while multithreading?

Question

I was messing around with the tqdm module and wanted to run simultaneous progress bars, so i made Thread objects as below

from tqdm import tqdm
import time
from threading import Thread

def func1():
    for i in tqdm(range(20)):
        time.sleep(0.1)

def func2():
    for j in tqdm(range(20)):
        time.sleep(0.3)

t1 = Thread(target=func1)
t2 = Thread(target=func2)

t1.start()
t2.start()

t2.join()
t1.join()

print('Completed')

The output starts with

But when thread t2 ends, it exchanges position with the bar display of t1 and t1 runs till it ends.

I don't want the bars to exchange positions

I tried interchanging the positions of lines of starting and joining of threads but it leads to re printing of t1 bar once t2 finishes like this

To analyse these problems i would recommend trying running these codes for yourself.

Can someone tell me why these both things are happening and how to fix it?

Answer 1

One solution could be updating all bars in separate thread (using Queue to get which bar should be updated next):

import time
import queue
from tqdm import tqdm
from threading import Thread

bars_queue = queue.Queue()


def func1():
    for i in range(20):
        bars_queue.put_nowait(0)  # update bar 0
        time.sleep(0.1)


def func2():
    for j in range(20):
        bars_queue.put_nowait(1)  # update bar 1
        time.sleep(0.3)


def bars_handler():
    bars = [tqdm(total=20, position=i) for i in range(2)]
    while True:
        i = bars_queue.get()  # which bar should I update next?
        bars[i].update()
        bars[i].refresh()


bars_thread = Thread(target=bars_handler, daemon=True) # daemon=True so we don't have to use .join()
bars_thread.start()

t1 = Thread(target=func1)
t2 = Thread(target=func2)

t1.start()
t2.start()

t2.join()
t1.join()

print("{}Completed".format("\n" * 2))

Prints correctly the bars:

100%|██████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████| 20/20 [00:01<00:00, 10.09it/s]
100%|██████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████| 20/20 [00:05<00:00,  3.33it/s]
Completed