Without knowing how much work there is, a ProgressBar has nothing to divide the current value by, so it cannot show a percentage or estimate how long is left. This step tells it the total up front so it can show both.

.. demo:: tutorial/step3

The previous step's ProgressBar() call took no arguments, so the bar rendered as an indeterminate display -- there was no way to know how far through the work it was. Here the constructor gains a max_value=100 argument: progressbar.ProgressBar(max_value=100). Nothing else about the loop changes -- bar.update(i + 1) is called exactly as before -- but knowing the total lets the bar compute a percentage and an ETA from each update instead of just showing that something is happening.

Next: :doc:`step4`.