tqdm progressbar and zip built-in do not work together

Question

tqdm is a Python module to easily print in the console a dynamically updating progressbar. For example

from tqdm import tqdm from time import sleep for _ in tqdm(range(10)):      sleep(0.1)  

prints a dynamic progressbar in the console for 1sec as the iteration executes:

I have not figured out how to use tqdm with the builtin zip object.
The use case of this would be to iterate over two corresponding lists with a console progressbar.
For example, I would expect this to work:

for _, _ in tqdm(zip(range(10), range(10))):     sleep(0.1) 

but the progressbar printed to the console in this case is not correct:

A workaround is to use tqdm with enumerate, however then an iterator index must be defined and managed.

Answer 1

tqdm can be used with zip if a total keyword argument is provided in the tqdm call.

The following example demonstrates iteration over corresponding elements in two lists with a working __tqdm__ progress bar for the case where a total keyword argument is used:

The issue is that tqdm needs to know the length of the iterable ahead of time. Because zip is meant to handle iterables with different lengths, it does not have as an attribute a single length of its arguments.

So, __tqdm__ still works nicely with zip, you just need to provide a little manual control with the total keyword argument.

Answer 2

Using tqdm>=4.42.0, you should do:

from tqdm.contrib import tzip from time import sleep  for _, _ in tzip(range(10), range(10)):     sleep(0.1) 

Just to note in https://github.com/tqdm/tqdm#faq-and-known-issues:

• Wrapping generators:
  • Generator wrapper functions tend to hide the length of iterables. tqdm does not.
  • Replace tqdm(enumerate(...)) with enumerate(tqdm(...)) or tqdm(enumerate(x), total=len(x), ...). The same applies to numpy.ndenumerate.
  • Replace tqdm(zip(a, b)) with zip(tqdm(a), b) or even zip(tqdm(a), tqdm(b)).
  • The same applies to itertools.
  • Some useful convenience functions can be found under tqdm.contrib.