dragoncurve.py

# dragoncurve.py
# Written by Eli Blaney
#
# Draws the dragon curve.
# Uses Python 3.
#
# Copyright (c) 2019 Eli Blaney.
# Licensed under WTFPL.
# www.wtfpl.net

import turtle

# Helper funciton to create the
# turtle that will draw the dragon curve
def createTurtle():
    t = turtle.Turtle()
    t.ht()
    t.speed(0)
    t.right(90)
    return t

### This is algorithm 1, taken from Wikipedia.   ###
### It uses a formula to calculate the direction ###
### of each step of the dragon curve.            ###

def formulaDragon(step_size):
    t = createTurtle()
    n = 0
    while(True):
        turn = (((n & -n) << 1) & n) != 0
        if(turn):
            t.left(90)
        else:
            t.right(90)
        t.forward(step_size)
        n += 1

### This is my original algorithm to ###
### calculate the dragon curve. It   ###
### is based on R/L sequence logic   ###

# Creates each iteration of directions
def nextDragon(str):
    if(len(str) == 0):
        return "R";
    swap = lambda c : ("L" if c == "R" else "R")
    return str + "R" + "".join(list(map(swap, str[::-1])))

# Compiles the iterations and draws the curve
def dragon(step_size, instant, iterations):
    t = createTurtle()
    if(instant):
        turtle.tracer(0, 0)

    path = nextDragon('')
    for _ in range(iterations):
        path = nextDragon(path)

    for c in path:
        if c == "R":
            t.right(90)
            t.forward(step_size)
        elif c == "L":
            t.left(90)
            t.forward(step_size)

    turtle.update()

### PROGRAM ENTRANCE POINT ###

# Formulaic algorithm = wikipedia formula = formulaDragon
inputChoice = input("Enable formulaic algorithm? (Y/n) ").lower()
choice = inputChoice != "n" and inputChoice != "no" and inputChoice != "false"

if(choice):
    
    # Because the formulaic algorithm executes infinitely,
    # iterations and fast render mode aren't applicable

    # Step size = length of each line
    step_size = int(input("Step size: "))

    formulaDragon(step_size)

else:

    # Fast render = disable turtle rendering until finished
    inputInstant = input("Fast render? (y/N) ").lower()
    instant = not (inputInstant != "y" and inputInstant != "yes" and inputInstant != "true")

    # Step size = length of each line
    step_size = int(input("Step size: "))

    # Iterations = how many dragon curve sequences
    # to generate before stopping execution
    iterations = int(input("Iterations: "))

    dragon(step_size, instant, iterations)

### PROGRAM EXIT ###

input("Press enter to continue...")