Python Turtle Lindermayer System

lindenmayerSystem.py

#!/usr/bin/python                                                                                               
                                                                                                                
import turtle                                                                                                   
                                                                                                                
system = {                                                                                                      
  'a': ['b','|','c'],                                                                                           
  'b': ['b'],                                                                                                   
  'c': ['b','|','d'],                                                                                           
  'd': ['e','/','d'],                                                                                           
  'e': ['f'],                                                                                                   
  'f': ['g'],                                                                                                   
  'g': ['h',['a']],                                                                                             
  'h': ['h']                                                                                                    
  }                                                                                                             
                                                                                                                
drawcmd = {                                                                                                     
  'a': 'f:500',                                                                                                 
  'b': 'r:45,f:1000',                                                                                           
  'c': 'r:45,f:150',                                                                                            
  'd': 'r:45,f:110',                                                                                            
  'e': 'r:45,f:500,l:45',                                                                                       
  'f': 'l:45,f:400,l:7,f:320',                                                                                  
  'g': 'l:45,f:100,r:90,f:320',                                                                                 
  'h': 'r:45,f:500',                                                                                            
  '|': 'r:30,f:400',                                                                                            
  '/': 'l:30,f:300,r:45,f:200,r:45,f:100',                                                                      
                                                                                                                
}                                                                                                               
                                                                                                                
                                                                                                                
#turtle.screensize(1920,1080)                                                                                   
turtle.setworldcoordinates(-5000,-5000, 5000,5000)                                                              
                                                                                                                
turtles = []                                                                                                    
                                                                                                                
globalt = turtle.Turtle()                                                                                       
#globalt.speed('fastest')                                                                                       
                                                                                                                
def push():                                                                                                     
  global turtles,globalt                                                                                        
  turtles.append( [globalt.pos(), globalt.heading()] )                                                          
                                                                                                                
def pop():                                                                                                      
  global turtles,globalt                                                                                        
  d = turtles.pop()                                                                                             
  currentPen = globalt.pen()                                                                                    
  globalt.pu()                                                                                                  
  globalt.setpos(d[0])                                                                                          
  globalt.setheading( d[1])                                                                                     
  globalt.pen(currentPen)                                                                                       
                                                                                                                
def draw(cmds):                                                                                                 
  global globalt                                                                                                
  for cmd in cmds:                                                                                              
    if type(cmd) is list:                                                                                       
      push()                                                                                                    
      #globalt.right(45)                                                                                        
      #globalt.forward(10)                                                                                      
      draw(cmd)                                                                                                 
      pop()                                                                                                     
    else:                                                                                                       
      if cmd in drawcmd:                                                                                        
        for dc in drawcmd[cmd].split(','):                                                                      
          (k,v) = dc.split(':')                                                                                 
          if k == 'd':                                                                                          
            globalt.dot(int(v))                                                                                 
          elif k == 'f':                                                                                        
            globalt.forward(int(v))                                                                             
          elif k == 'r':                                                                                        
            globalt.right(int(v))                                                                               
          elif k == 'l':                                                                                        
            globalt.left(int(v))                                                                                
          elif k == 'pu':                                                                                       
            globalt.pu()                                                                                        
          elif k == 'pd':                                                                                       
            globalt.pd()                                                                                        
                                                                                                                
                                                                                                                
                                                                                                                
def step(systemin):                                                                                             
  out = []                                                                                                      
  for cmd in systemin:                                                                                          
    if type(cmd) is list:                                                                                       
      out.append( step(cmd) )                                                                                   
    elif cmd in system:                                                                                         
      out = out + system[cmd]                                                                                   
  return out                                                                                                    
                                                                                                                
a = ['a']                                                                                                       
                                                                                                                
for i in range(40):                                                                                             
  a = step(a)                                                                                                   
                                                                                                                
#print a                                                                                                        
turtle.tracer(1000,0)                                                                                           
draw(a)                                                                                                         
                                                                                                                
                                                                                                                
                                                                                                                
#turtle.onscreenclick(update)                                                                                   
#turtle.mainloop()                                                                                              
turtle.exitonclick()