Drawing with Python

turtle is a pen that obeys commands: forward(100), right(90), penup(), pendown().

import turtle
t = turtle.Turtle()
for _ in range(4):
    t.forward(100)
    t.right(90)          # a square

The rule for regular shapes: n sides → turn 360/n degrees each time. A triangle: 360/3 = 120°. A pentagon: 72°. A circle: 360 steps of 1°.

Patterns appear when the loop variable is used in the command:

import turtle
t = turtle.Turtle(); t.speed(0)

for i in range(60):
    t.forward(i * 3)      # the length grows → a spiral
    t.right(91)           # 91 instead of 90 → the shape rotates

Swap 91 for 90 and you get a square that grows. Swap it for 120 and you get a triangular spiral. A single digit changes the whole picture.

Without turtle (in the browser, say): the same idea works with matplotlib, or by working out the coordinates yourself with sin and cos. The point is the same — a loop plus a small change per lap gives you a pattern.