tqdm progressbar and zip built-in do not work together

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.

Using tqdm>=4.42.0, you should do:

from tqdm.contrib import tzipfrom time import sleepfor _, _ 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.

For you have a progress-bar is expected that you can predict the length of your data structure.

range implements the hook method __len__, so you can discover the length doing built-in len

>>> dir(range(10))[ '__le__', '__class__', '__contains__', '__delattr__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__getitem__', '__gt__', '__hash__', '__init__', '__iter__', '__len__', '__lt__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__reversed__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', 'count', 'index', 'start', 'step', 'stop']>>> len(range(10))10

zip, however, does not provide a way to guess the length of the wrapped structure, so probably that's why because tqdm can not show the progress bar.

dir(zip(range(10))) # no __len__ here['__class__', '__delattr__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__gt__', '__hash__', '__init__', '__iter__', '__le__', '__lt__', '__ne__', '__new__', '__next__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__']>>> len(zip(range(10)))Traceback (most recent call last):  File "<stdin>", line 1, in <module>TypeError: object of type 'zip' has no len()

Edit:

Yeah, that's it. Look the docs

...

Wrapping enumerated iterables: use enumerate(tqdm(...)) instead of tqdm(enumerate(...)). The same applies to numpy.ndenumerate. This is because enumerate functions tend to hide the length of iterables. tqdm does not.

...

Manual control on tqdm() updates by using a with statement:

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

If the optional variable total (or an iterable with len()) is provided, predictive stats are displayed.

with is also optional (you can just assign tqdm() to a variable, but in this case don't forget to del or close() at the end:

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