Quadrati 2 – 3 – 4

import math
import turtle

WIDTH  = 500
HEIGHT = 500
r2     = math.sqrt(2)/2
DIM1   = 0.8*HEIGHT
DIM2   = r2*DIM1
PASSI  = [DIM1,DIM1,DIM1,DIM1/2,DIM2,DIM2,DIM2,DIM2,DIM1/2]
ANGOLI = [   0,  90,  90,    90,  45,  90,  90,  90,    45]

turtle.setup(WIDTH, HEIGHT)
turtle.title("Un solo tratto")
turtle.shape('turtle')
turtle.pencolor('red')
turtle.bgcolor('pink')
turtle.pensize(4)

turtle.penup()
turtle.setposition(-DIM1/2, -DIM1/2)
turtle.pendown()

for angolo, passo in zip(ANGOLI, PASSI):
    turtle.left(angolo)
    turtle.forward(passo)

...
DIM1 = 0.8*HEIGHT
DIM2 = r2*DIM1
DIM3 = r2*DIM2
...

...
DIM1 = 0.8*HEIGHT
DIM2 = r2*DIM1
DIM3 = r2*DIM2
DIM4 = r2*DIM3
...