import turtle
def createLSystem(numIters, axiom):
startString = axiom
endString = ""
for i in range(numIters):
endString = processString(startString)
startString = endString
return endString
def processString(oldStr):
newstr = ""
for ch in oldStr:
newstr = newstr + applyRules(ch)
return newstr
def applyRules(ch):
newstr = ""
if ch == 'F':
newstr = 'FF' # Rule 1
elif ch == 'X':
newstr = '--FXF++FXF++FXF--'
else:
newstr = ch # no rules apply so keep the character
return newstr
def drawLsystem(aTurtle, instructions, angle, distance):
for cmd in instructions:
if cmd == 'F':
aTurtle.forward(distance)
elif cmd == 'B':
aTurtle.backward(distance)
elif cmd == '+':
aTurtle.right(angle)
elif cmd == '-':
aTurtle.left(angle)
def main():
inst = createLSystem(5, "FXF--FF--FF") # create the string
print(inst)
t = turtle.Turtle() # create the turtle
wn = turtle.Screen()
t.up()
t.back(200)
t.right(90)
t.forward(100)
t.left(90)
t.down()
t.speed(9)
drawLsystem(t, inst, 60, 5) # draw the picture
# angle 90, segment length 5
wn.exitonclick()
main()