Show a custom value next to the bar

Sometimes the bar’s own progress isn’t the only number worth showing – a current filename, a running total, or any other value your loop computes – and that value doesn’t come from value/max_value at all.

"""Recognize `DynamicMessage` in old code as today's `Variable`.

Older code may still import `DynamicMessage` -- it is a plain subclass of
`Variable` kept for compatibility, not a different widget. Prefer
`Variable` in new code; this example updates one of each, side by side
from the same value, to show they behave identically.
"""

import random
import time

import progressbar

random.seed(0)

STEPS = 24


def main() -> None:
    widgets = [
        progressbar.Percentage(),
        ' ',
        progressbar.Bar(),
        ' ',
        progressbar.Variable('current'),
        ' ',
        progressbar.DynamicMessage('legacy'),
    ]
    with progressbar.ProgressBar(max_value=STEPS, widgets=widgets) as bar:
        for step in range(STEPS):
            value = random.random()
            bar.update(step + 1, current=value, legacy=value)
            time.sleep(0.005)


if __name__ == '__main__':
    main()

Variable(name) renders a named entry from bar.update()’s keyword arguments: pass current=some_value to update() and a Variable('current') widget picks it up on the next redraw. You don’t need to seed it in advance – the bar scans its widget list at construction and registers a placeholder for every named variable that isn’t already supplied, so the first render shows dashes rather than raising. Older code may import DynamicMessage instead: it is a plain subclass of Variable, kept only so existing imports keep working, and behaves identically – prefer Variable in anything new.