I've been a fan of the tqdm Python module for quite some time, but I found it difficult to find a reason to use it; generally, loops run fast enough that a progress bar is unnecessary. However, I found a perfect use for it in reading large files.

If the task isn't something I can speed up via multiprocessing, I can use tqdm to decide whether I can grab a cup of coffee or work on something else while I let it run. tqdm allows me to easily add a progress bar to the read operation, like so:

with open(file_path) as file:
for line in tqdm(file, total=get_num_lines(file_path)):
# various operations here


As you can see, adding this functionality is as simple as wrapping the file with the tqdm method. However, to display the progress bar, tqdm needs an idea of how many total lines it needs to process. I use this code snippet from StackOverflow to quickly find this information when instantiating the progress bar:

import mmap

def get_num_lines(file_path):
fp = open(file_path, "r+")
buf = mmap.mmap(fp.fileno(), 0)
lines = 0