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Text and Maths

Words and equations are shapes too: write, move, colour and change them.

Text

from pymations import *

hello = Text("Hello!", font_size=72, color=YELLOW)
play(Write(hello))
OptionWhat it does
font_size=48The size; 48 is normal, 96 is twice as big
color=BLUEThe colour (white unless you say)
weight=BOLDBold
slant=ITALICItalic
t2c={"world": BLUE}Colours every place a word appears
font="serif"A serif font (the one maths is written in)
font="mono"A typewriter font, every letter the same width

Text uses built-in fonts, the same on every device, so a video looks the same wherever it is made: a clear sans-serif unless you say, "serif" or "mono". A family name picks the nearest of the three ("Courier" is mono, "Georgia" is serif).

To use your own font, put its file next to the .py file and give its name: Text("Hello", font="Brand.ttf"). .ttf, .otf and .woff2 files work.

text[0] is the first letter (spaces are not counted), so single letters can be coloured or moved.

Maths: MathTex

MathTex writes maths the way LaTeX does:

from pymations import *

formula = MathTex(r"\frac{-b \pm \sqrt{b^2 - 4ac}}{2a}", font_size=72)
play(Write(formula))
wait()
  • Put r before the quotes (r"..."). Without it, Python reads \f and \b as special characters.
  • Powers are x^2, x^{10}; below is x_1; fractions \frac{a}{b}; roots \sqrt{x}; Greek letters \pi, \theta, \alpha.
  • Maths is laid out by KaTeX, which understands most of the LaTeX used in maths: fractions, roots, sums, integrals, limits, matrices, \text{...} and \tfrac. A few rare LaTeX packages are not available; if a formula can't be read, the output under the preview says which part.

Parts of an equation

Give MathTex several strings and each one becomes a part you can reach by number:

from pymations import *

eq = MathTex("a^2", "+", "b^2", "=", "c^2", font_size=72)
eq[0].set_color(BLUE)
eq[2].set_color(GREEN)
eq[4].set_color(YELLOW)

play(Write(eq))
play(Indicate(eq[4]))
wait()

Double braces split one string into parts too: MathTex("{{ a^2 }} + {{ b^2 }} = {{ c^2 }}") has five parts, the same as above.

WayWhat it does
eq[2]The third part
eq.get_part_by_tex("b^2")The first part containing b^2
eq.set_color_by_tex("b", GREEN)Colours every part containing b
MathTex("x + y", tex_to_color_map={"x": BLUE})Makes x its own part and colours it
MathTex("x + y = 1", substrings_to_isolate=["x"])Makes x its own part, to colour or move later

Changing one equation into another

TransformMatchingTex moves the parts that appear in both equations to their new places, and fades the rest in and out. It is the usual way to show algebra steps:

from pymations import *

before = MathTex("x", "+", "3", "=", "5", font_size=72)
after = MathTex("x", "=", "5", "-", "3", font_size=72)

play(Write(before))
wait()
play(TransformMatchingTex(before, after))
wait()

Parts match when their text is the same, so split equations so that the pieces you want to move are their own parts. Transform(before, after) changes the whole shape instead, without matching.

Tex: words with maths inside

Tex is for sentences, with maths between dollar signs:

from pymations import *

line = Tex(r"The area is $\pi r^2$")
play(Write(line))

Title("Chapter 1") is a Tex placed at the top of the picture.

Numbers

DecimalNumber(3.14159, num_decimal_places=2) shows 3.14. Integer(42) shows a whole number.

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