[increasing a number in steps] How to increase a DecimalNumber in discrete steps in an animation. #manim #decimalnumber #updater #valuetracker

20250603_decnum.py

from manim import *

# https://discord.com/channels/581738731934056449/1379443317175091252/1379443317175091252
class Test(Scene):
    def construct(self):
        numbers = [100]*10
        numbersVG = VGroup(Text(str(n)) for n in numbers)
        numbersVG.arrange(RIGHT).shift(1.3 * DOWN)
        self.add(numbersVG)

        tally = DecimalNumber(0, num_decimal_places=0).to_edge(UP)
        vt = ValueTracker(0)
        def tally_updater(mobj):
            tally.set_value(vt.get_value())
        tally.add_updater(tally_updater, call_updater=True)
        self.add(tally)

        time = 1
        dt = 0.2

        animations = []
        for i, elem in enumerate(numbersVG):
            animation_group = AnimationGroup(
                FadeOut(
                    elem,
                    shift=tally.get_center() - elem.get_center(),
                    run_time=time
                ),
                # FadeOut(# the square #),
            )
            animations.append(animation_group)

        def step(t):
            dy = 1/np.sum(numbers)
            dt = 1/(len(numbers)+2)
            n = min(int(t/dt),len(numbers)+1)
            part = np.sum(numbers[:n])
            return part*dy

        self.play(
            LaggedStart(*animations, lag_ratio=dt),
            vt.animate(run_time=time*(1+len(numbers)*dt), rate_func=step).set_value(np.sum(numbers))
        )
        self.wait(0.5)

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