变量¶

限定名称: manim.mobject.text.numbers.Variable

class Variable(var, label, var_type=<class 'manim.mobject.text.numbers.DecimalNumber'>, num_decimal_places=2, **kwargs)[来源]¶

基础类: VMobject

一个用于显示文本的类，该文本显示“标签 = 值”，并且值从ValueTracker持续更新。

Parameters:

var (float) – 您需要跟踪和显示的初始值。
标签 (str | Tex | MathTex | 文本 | SingleStringMathTex) – 你的变量的标签。原始字符串会被转换为 MathTex 对象。
var_type (DecimalNumber | 整数) – 用于显示数字的类。默认为 DecimalNumber。
num_decimal_places (int) – 变量中显示的小数位数。默认为2。如果 var_type 是 Integer，则忽略此参数。
kwargs – 传递给 ~.Mobject 的其他参数。

label¶

你的变量的标签，例如 x = ...。

Type:: 联合[str, Tex, MathTex, 文本, SingleStringMathTex]

tracker¶

在屏幕上更新变量的值时非常有用。

Type:: ValueTracker

value¶

您的变量值的文本。

Type:: 联合[DecimalNumber, Integer]

示例

正常用法：

# DecimalNumber type
var = 0.5
on_screen_var = Variable(var, Text("var"), num_decimal_places=3)
# Integer type
int_var = 0
on_screen_int_var = Variable(int_var, Text("int_var"), var_type=Integer)
# Using math mode for the label
on_screen_int_var = Variable(int_var, "{a}_{i}", var_type=Integer)

示例：VariablesWithValueTracker ¶

from manim import *

class VariablesWithValueTracker(Scene):
    def construct(self):
        var = 0.5
        on_screen_var = Variable(var, Text("var"), num_decimal_places=3)

        # You can also change the colours for the label and value
        on_screen_var.label.set_color(RED)
        on_screen_var.value.set_color(GREEN)

        self.play(Write(on_screen_var))
        # The above line will just display the variable with
        # its initial value on the screen. If you also wish to
        # update it, you can do so by accessing the `tracker` attribute
        self.wait()
        var_tracker = on_screen_var.tracker
        var = 10.5
        self.play(var_tracker.animate.set_value(var))
        self.wait()

        int_var = 0
        on_screen_int_var = Variable(
            int_var, Text("int_var"), var_type=Integer
        ).next_to(on_screen_var, DOWN)
        on_screen_int_var.label.set_color(RED)
        on_screen_int_var.value.set_color(GREEN)

        self.play(Write(on_screen_int_var))
        self.wait()
        var_tracker = on_screen_int_var.tracker
        var = 10.5
        self.play(var_tracker.animate.set_value(var))
        self.wait()

        # If you wish to have a somewhat more complicated label for your
        # variable with subscripts, superscripts, etc. the default class
        # for the label is MathTex
        subscript_label_var = 10
        on_screen_subscript_var = Variable(subscript_label_var, "{a}_{i}").next_to(
            on_screen_int_var, DOWN
        )
        self.play(Write(on_screen_subscript_var))
        self.wait()

class VariablesWithValueTracker(Scene):
    def construct(self):
        var = 0.5
        on_screen_var = Variable(var, Text("var"), num_decimal_places=3)

        # You can also change the colours for the label and value
        on_screen_var.label.set_color(RED)
        on_screen_var.value.set_color(GREEN)

        self.play(Write(on_screen_var))
        # The above line will just display the variable with
        # its initial value on the screen. If you also wish to
        # update it, you can do so by accessing the `tracker` attribute
        self.wait()
        var_tracker = on_screen_var.tracker
        var = 10.5
        self.play(var_tracker.animate.set_value(var))
        self.wait()

        int_var = 0
        on_screen_int_var = Variable(
            int_var, Text("int_var"), var_type=Integer
        ).next_to(on_screen_var, DOWN)
        on_screen_int_var.label.set_color(RED)
        on_screen_int_var.value.set_color(GREEN)

        self.play(Write(on_screen_int_var))
        self.wait()
        var_tracker = on_screen_int_var.tracker
        var = 10.5
        self.play(var_tracker.animate.set_value(var))
        self.wait()

        # If you wish to have a somewhat more complicated label for your
        # variable with subscripts, superscripts, etc. the default class
        # for the label is MathTex
        subscript_label_var = 10
        on_screen_subscript_var = Variable(subscript_label_var, "{a}_{i}").next_to(
            on_screen_int_var, DOWN
        )
        self.play(Write(on_screen_subscript_var))
        self.wait()

示例：VariableExample ¶

from manim import *

class VariableExample(Scene):
    def construct(self):
        start = 2.0

        x_var = Variable(start, 'x', num_decimal_places=3)
        sqr_var = Variable(start**2, 'x^2', num_decimal_places=3)
        Group(x_var, sqr_var).arrange(DOWN)

        sqr_var.add_updater(lambda v: v.tracker.set_value(x_var.tracker.get_value()**2))

        self.add(x_var, sqr_var)
        self.play(x_var.tracker.animate.set_value(5), run_time=2, rate_func=linear)
        self.wait(0.1)

class VariableExample(Scene):
    def construct(self):
        start = 2.0

        x_var = Variable(start, 'x', num_decimal_places=3)
        sqr_var = Variable(start**2, 'x^2', num_decimal_places=3)
        Group(x_var, sqr_var).arrange(DOWN)

        sqr_var.add_updater(lambda v: v.tracker.set_value(x_var.tracker.get_value()**2))

        self.add(x_var, sqr_var)
        self.play(x_var.tracker.animate.set_value(5), run_time=2, rate_func=linear)
        self.wait(0.1)

方法

属性

`animate`	用于动画化`self`的任何方法的应用。
`animation_overrides`
`color`
`depth`	mobject的深度。
`fill_color`	如果有多种颜色（用于渐变），则返回第一个颜色
`height`	mobject的高度。
`n_points_per_curve`
`sheen_factor`
`stroke_color`
`width`	mobject的宽度。

_original__init__(var, label, var_type=<class 'manim.mobject.text.numbers.DecimalNumber'>, num_decimal_places=2, **kwargs)¶

初始化自身。有关准确的签名，请参阅 help(type(self))。

Parameters:

var (浮点数)
标签 (字符串 | Tex | MathTex | 文本 | SingleStringMathTex)
var_type (DecimalNumber | 整数)
num_decimal_places (int)