# manim.mobject.value_tracker.ValueTracker¶

class ValueTracker(value=0, **kwargs)[source]

A mobject that can be used for tracking (real-valued) parameters. Useful for animating parameter changes.

Not meant to be displayed. Instead the position encodes some number, often one which another animation or continual_animation uses for its update function, and by treating it as a mobject it can still be animated and manipulated just like anything else.

Examples

Example: ValueTrackerExample

from manim import *

class ValueTrackerExample(Scene):
def construct(self):
number_line = NumberLine()
pointer = Vector(DOWN)
label = MathTex("x").add_updater(lambda m: m.next_to(pointer, UP))

pointer_tracker = ValueTracker(0)
lambda m: m.next_to(
number_line.n2p(pointer_tracker.get_value()),
UP
)
)
pointer_tracker += 1.5
self.wait(1)
pointer_tracker -= 4
self.wait(0.5)
self.play(pointer_tracker.animate.set_value(5)),
self.wait(0.5)
self.play(pointer_tracker.animate.set_value(3))
self.play(pointer_tracker.animate.increment_value(-2))
self.wait(0.5)


Note

You can also link ValueTrackers to updaters. In this case, you have to make sure that the ValueTracker is added to the scene by add

Example: ValueTrackerExample

from manim import *

class ValueTrackerExample(Scene):
def construct(self):
pointer_tracker = ValueTracker(0)
self.wait(2)


Methods

 get_value Get the current value of the ValueTracker. increment_value Increments (adds) a scalar value to the ValueTracker interpolate Turns self into an interpolation between mobject1 and mobject2. set_value Sets a new scalar value to the ValueTracker

Attributes

 animate Used to animate the application of a method. depth The depth of the mobject. height The height of the mobject. width The width of the mobject.
get_value()[source]

Get the current value of the ValueTracker. This value changes continuously when animate for the ValueTracker is called.

Return type

float

increment_value(d_value)[source]

Increments (adds) a scalar value to the ValueTracker

Parameters

d_value (float) –

interpolate(mobject1, mobject2, alpha, path_func=<function straight_path>)[source]

Turns self into an interpolation between mobject1 and mobject2.

set_value(value)[source]

Sets a new scalar value to the ValueTracker

Parameters

value (float) –