Python script for visualizing L Systems using turtle. Run it online: https://trinket.io/python/a050d41536

LSystems.py

import turtle

def main(lString):
    wn = turtle.Screen()
    kurt = turtle.Turtle()
    
    scheme = makeLSystem(lString)
    drawLSystem(kurt, scheme)

def makeLSystem(lString, times=5):
		seed = lString.split('\n')[0]
		acc = seed
		schema = lStringtoDict(lString)
		for i in range(times):
			acc = parse(acc, schema)
		return acc
    
def lStringtoDict(lString):
	lines = [line.split(' ') for line in lString.split('\n')[1:]]
	return {line[0] : line[-1] for line in lines}

def parse(scheme, schema):
	acc = ''
	for ch in scheme:
		if ch in schema.keys() :
			acc += schema[ch]
			continue
		acc += ch
	return acc


def drawLSystem(t, scheme,angle=25.7):
		infoList = []
		def convert(t, char, angle, lyst, dist=5):
			if char == 'F' : t.forward(dist)
			elif char == 'B' : t.backward(dist)
			elif char == '+' : t.left(angle)
			elif char == '-' : t.right(angle)
			elif char == '[' : 
				lyst.append([t.heading(), t.xcor(), t.ycor()])
			elif char == ']' : 
				tLoc = lyst.pop()
				t.seth(tLoc[0])
				t.setposition(tLoc[1], tLoc[2])
		for char in scheme:
			convert(t, char, angle, infoList)
    
if __name__ == '__main__':
    lString = '''H
H --> HFX[+H][-H]
X --> X[-FFF][+FFF]FX'''
    main(lString)
    

LSystems.txt

### First Line is the seed (and angle) to initialize the system
### Trailing lines are the rules for the L System
### Obtained from : https://runestone.academy/runestone/static/thinkcspy/Strings/Exercises.html


# Hilbert Curve
L
L -> +RF-LFL-FR+
R -> -LF+RFR+FL-

# Dragon Curve
FX 90
X -> X+YF+
Y -> -FX-Y

# Arrowhead Curve
YF 60
X -> YF+XF+Y
Y -> XF-YF-X

# Peano-Gosper Curve
FX 60
X -> X+YF++YF-FX--FXFX-YF+
Y -> -FX+YFYF++YF+FX--FX-Y

# The Sierpinski Triangle
FXF--FF--FF
F -> FF
X -> --FXF++FXF++FXF--

# Garden Herb
H 25.7
H --> HFX[+H][-H]
X --> X[-FFF][+FFF]FX

F 25
F --> F[-F]F[+F]F

X
X --> F[-X]+X
F --> FF