Color a bar, solid or gradient

Bars use a progress gradient by default, and spinners cycle through colours as they animate. Choose your own gradient or keep a spinner one colour when that better suits the surrounding output:

"""Choose a progress gradient and a solid colour for an animated spinner.

The bar follows its percentage. The spinner normally cycles through
colours with its frames. Passing one colour instead of a gradient
keeps it blue throughout the animation.
"""

import time

import progressbar
from progressbar.terminal import ColorGradient, colors
from progressbar.widgets import TGradientColors

STEPS = 24

HEALTH_GRADIENT = ColorGradient(colors.red, colors.yellow, colors.green)


def main() -> None:
    widgets = [
        progressbar.Percentage(),
        ' ',
        progressbar.Bar(
            gradient_colors=TGradientColors(fg=HEALTH_GRADIENT, bg=None),
        ),
    ]
    with progressbar.ProgressBar(max_value=STEPS, widgets=widgets) as bar:
        for step in range(STEPS):
            bar.update(step + 1)
            time.sleep(0.005)

    spinner_widgets = [
        'Scanning: ',
        progressbar.AnimatedMarker(
            gradient_colors=TGradientColors(fg=colors.blue, bg=None),
        ),
    ]
    with progressbar.ProgressBar(
        max_value=progressbar.UnknownLength, widgets=spinner_widgets
    ) as bar:
        for step in range(STEPS):
            bar.update(step + 1)
            time.sleep(0.005)


if __name__ == '__main__':
    main()

Pass gradient_colors=TGradientColors(fg=ColorGradient(...), bg=None) to Bar() to change the foreground colour as its percentage moves from 0 to 100. The first bar follows that gradient. The spinner uses gradient_colors=TGradientColors(fg=colors.blue, bg=None). A single colour keeps it blue while its characters continue to rotate.

For an unknown-length Bar or BouncingBar, use fixed_colors=TFixedColors(fg_none=..., bg_none=None) to choose its colour. AnimatedMarker follows its animation cycle instead of a percentage, so its gradient_colors works with or without a total.

Caveats

Whether either actually renders in color depends on what the terminal reports it supports – detected from COLORTERM/TERM, or forced with the PROGRESSBAR_ENABLE_COLORS environment variable (24bit, 256, or 16) when detection guesses wrong, such as under CI or when output is piped through something that strips the terminal type.

Pass enable_colors=False to ProgressBar to disable colours for the whole bar.