Nested tqdm outputs to new line

Question

When I try to use tqdm for nested loops, the loops update to new lines. The progress bar was working fine for just a single loop. I am running python 3.6.5. Is this an issue with the python version compatibility? If this is not currently possible in tqdm, how would I do this using another module?

I have tried using the progressbar module, but it had the same issue.

from tqdm import tqdm
from time import sleep
for i in tqdm(range(20), desc = 'sleeping'):
     for j in tqdm(range(15), desc = 'inside', leave = False):
        sleep(.1)

This is what I am getting as output:

sleeping:   0%|                                                                                 | 0/20 [00:00<?, ?it/s]
inside:   0%|                                                                                   | 0/15 [00:00<?, ?it/s]
inside:   7%|█████                                                                      | 1/15 [00:00<00:01,  9.94it/s]
inside:  13%|██████████                                                                 | 2/15 [00:00<00:01,  9.94it/s]
inside:  20%|███████████████                                                            | 3/15 [00:00<00:01,  9.91it/s]
inside:  27%|████████████████████                                                       | 4/15 [00:00<00:01,  9.88it/s]
inside:  33%|█████████████████████████                                                  | 5/15 [00:00<00:01,  9.86it/s]
inside:  40%|██████████████████████████████                                             | 6/15 [00:00<00:00,  9.84it/s]
inside:  47%|███████████████████████████████████                                        | 7/15 [00:00<00:00,  9.86it/s]
inside:  53%|████████████████████████████████████████                                   | 8/15 [00:00<00:00,  9.87it/s]
inside:  60%|█████████████████████████████████████████████                              | 9/15 [00:00<00:00,  9.88it/s]
inside:  67%|█████████████████████████████████████████████████▎                        | 10/15 [00:01<00:00,  9.88it/s]
inside:  73%|██████████████████████████████████████████████████████▎                   | 11/15 [00:01<00:00,  9.87it/s]
inside:  80%|███████████████████████████████████████████████████████████▏              | 12/15 [00:01<00:00,  9.86it/s]
inside:  87%|████████████████████████████████████████████████████████████████▏         | 13/15 [00:01<00:00,  9.85it/s]
inside:  93%|█████████████████████████████████████████████████████████████████████     | 14/15 [00:01<00:00,  9.86it/s]
inside: 100%|██████████████████████████████████████████████████████████████████████████| 15/15 [00:01<00:00,  9.84it/s]
sleeping:   5%|███▋                                                                     | 1/20 [00:01<00:28,  1.52s/it]

I expected this would only produce 2 progress bars of output.

Answer 1

The key is the inner loop and tqdm(your iterator) also returns a iterator. You can think it as the combination of your iterator and a process bar.

Therefore, when it exhausted, next loop will create a new tqdm iterator and consequently, new line.

My solution is do not use tqdm as your iterator and just use it as process bar.

outter_bar = tqdm(range(20), desc = 'sleeping')
outter_loop = range(20)

inner_bar = tqdm(range(15), desc = 'inside', leave = False)
inner_loop = range(15)

for i in outter_loop:
    outter_bar.update(1)
    for j in inner_loop:
        inner_bar.update(1)
        sleep(0.5)
    inner_bar.reset()

I test my code on jupyter notebook and it works.

Hope it helpful!

PS: To control various inner loop

outter_loop = tqdm(range(2))
inner = [range(10), range(15)]
inner_bar = tqdm(None, total=10)

for i in outter_loop:
    inner_bar.total = len(inner[i])
    for _ in inner[i]:
        sleep(0.5)
        inner_bar.update(1)
    inner_bar.reset()

Answer 2

As Windows terminal does not allow for ANSI escape character sequences, another module must be installed to make nested tqdm work on Windows. Installing colorama solved this problem for me.