When using Python to perform time-consuming operations, it is common to use a progress bar to visualize the progress. tqdm in Python is used to achieve this function.

First, let’s see the effect of tqdm’s progress bar.

Basic tqdm usage

There are 3 main uses of tqdm, automatic control, manual control or for scripting or command line.

Automatically controlled operation

The most basic usage, wrapping tqdm() directly around an arbitrary iterator.

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from tqdm import tqdm
import time

text = ""
for char in tqdm(["a", "b", "c", "d"]):
    text = text + char
    time.sleep(0.5)

trange(i) is a specially optimized instance of tqdm(range(i)).

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from tqdm import trange
import time

for i in trange(100):
    time.sleep(0.1)

If instantiated outside the loop, manual control of tqdm() can be allowed.

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from tqdm import tqdm
import time

pbar = tqdm(["a", "b", "c", "d"])
for char in pbar:
    pbar.set_description("Processing %s" % char)
    time.sleep(0.5)

Manual control of the run

Manually control the update of tqdm() with the with statement.

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from tqdm import tqdm
import time

with tqdm(total=100) as pbar:
    for i in range(10):
        pbar.update(10)
        time.sleep(0.5)

Or without the with statement, but with the del or close() method at the end.

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from tqdm import tqdm
import time

pbar = tqdm(total=100)
for i in range(10):
    pbar.update(10)
    time.sleep(0.5)
pbar.close()

The tqdm.update() method is used to manually update the progress bar and is useful for streaming operations such as reading files.

tqdm advanced applications

tqdm in a multi-process scenario

Code example.

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from multiprocessing import Pool
import tqdm
import time

def _foo(my_number):
   square = my_number * my_number
   time.sleep(1)
   return square 

if __name__ == '__main__':
   with Pool(2) as p:
      r = list(tqdm.tqdm(p.imap(_foo, range(30)), total=30))

Reference link.