A fractal turtle L-system thing

my_turtle.py

"""Fancy turtle L-system thing

Messing around at lunchtime :)

Inspired by https://bitaesthetics.com/posts/fractal-generation-with-l-systems.html"""

# Maybe this runs under Python 2? Who knows? Not sure what the turtle
# changes between 2 and 3 are
from __future__ import print_function


dawg = "Yo dawg, I heard you like fractals, so I put a fractal on your fractal so you can fractal while you fractal"
dawg_bit = "put a fractal on your fractal so you can fractal while you fractal"
new_dawg = dawg.replace("fractal", dawg_bit)
for i in range(2):
    new_dawg = new_dawg.replace("fractal", dawg_bit)
print(new_dawg)


import turtle


def set_up():
    # Length constant
    LENGTH = 250

    turtle.clear()
    turtle.screensize(LENGTH*4, LENGTH*4)

    # center square on the middle of the screen
    turtle.penup()
    turtle.goto(LENGTH, -LENGTH)
    turtle.pendown()

    turtle.setheading(180)  # face west/left
    #turtle.delay(1)         # go fast
    #turtle.delay(0.1)         # go really fast
    turtle.delay(0)         # go really really fast
    
    return LENGTH

LENGTH = setup()


def interpret(command):
    """Given a string command like "F100" or "R90", make the turtle do its thing.
    
    Handles lists of commands (and lists-of-lists, etc.)"""
    if type(command) == list:
        return [interpret(c) for c in command]

    if command[0].lower() not in "fblrz":
        # "comment/debug"
        return
        
    number = float(command[1:])
    do = command[0].lower()
    #print(command, "==>", do, number, type(number))
    
    if do == 'f':
        turtle.forward(number)
    if do == 'z':   # immutable forward command
        turtle.pencolor("red")
        turtle.forward(number)
        turtle.pencolor("black")
    if do == 'b':
        turtle.back(number)
    if do == 'l':
        turtle.left(number)
    if do == 'r':
        turtle.right(number)


def complexify_square(command):
    """Make a command more fractalish (squares)"""
    # handle lists of commands (and lists-of-lists, etc.)
    if type(command) == list:
        return [complexify_square(c) for c in command]
        
    if command[0].lower() not in "fblrz":
        # "comment/debug", but don't eat it
        return [command]
    
    number = float(command[1:])
    do = command[0].lower()
    if do == 'f':
        # turn forward into a square zig-zag
        #    ==>  _
        # __     | |_
        half = number / 2.0
        do_bit = "f" + str(half)
        return ["l90", do_bit, "r90", do_bit, "r90", do_bit, "l90", "z"+str(half), "-"]
    else:
        return [do+str(number)]


### dodecagon
#turtle_commands = ["F250", "R30.0"] * 12
#print(turtle_commands)
#
#for each_command in turtle_commands:
#    interpret(each_command)


### square
#turtle_commands = ["F500", "R90.0"] * 4
#print(turtle_commands)
#
#for each_command in turtle_commands:
#    interpret(each_command)


### old style, manually pulling/flattening commands from result
### (That's the `new_commands += ....` bit)
"""
commands = ["F"+str(LENGTH), "R90"]

for i in range(10):    
    new_commands = []
    for command in commands:
        new_commands += complexify_square(command)
    commands = new_commands
    print(' '.join(commands))
    for i in range(4):
        for each_command in commands:
            interpret(each_command)
"""

### New, can-handle-nested-lists style
commands = ["F"+str(LENGTH), "R90"]

# only go until length < 1.0 (it's too small to see after this)
length = LENGTH

while 1:
    new_commands = []
    for command in commands:
        new_commands += complexify_square(command)
    commands = new_commands
    
    length = length / 2.0
    if length < 1.0:
        # now print, and exit the loop
        # print(commands)
        print(len(commands),"commands created, length is", length)
        interpret(commands)


### Wheee, dodecagon fractal square
"""
commands = ["F"+str(LENGTH/3), "R30"]

for i in range(12):
    new_commands = []
    for command in commands:
        new_commands += complexify_square(command)
    commands = new_commands
    interpret(commands)
"""

    
ignored = input("Hit enter to exit")