Python Turtle for 循环无限运行答案

【问题标题】：Python Turtle for loop running infinitelyPython Turtle for 循环无限运行
【发布时间】：2019-05-07 07:45:10
【问题描述】：

我有一些之前成功运行的 Turtle 代码，用于在 Repl.it 的 Python 中使用 Turtle IDE 绘制 Sierpinski 垫片，但最近当我尝试再次运行它时，它成功地完成了所有操作，除非它击中for 循环，turtle 刚刚开始旋转，直到很久以后才执行 for 循环中的行。

我在 forloop 中添加了一个 print(i)，它重复打印 0，就好像它是一个无限循环

import turtle
from turtle import *

t = Turtle()
t.speed(0)
t.shape('turtle')
t.color('dark green')

def SGRules(char):
  if char == 'F':
    return 'F+F-F-F+F'
  else:
    return char

def processStr(oldstr, Fractal_Rules):
  newstr = ""
  for char in oldstr:
    newstr = newstr + Fractal_Rules(char)
  return newstr

def createLSystem(iteration, axiom, Fractal_Rules):
  startstr = axiom
  endstr = ""
  for i in range(iteration):
    endstr = processStr(startstr, Fractal_Rules)
    startstr = endstr
  return endstr

def drawLSystem(aturtle, lsys, angle, length):
  for cmd in lsys:
    if cmd == 'F':
      aturtle.forward(length)
    elif cmd == '+':
      aturtle.left(angle)
    elif cmd == '-':
      aturtle.right(angle)

sgstr = createLSystem(4, 'F', SGRules)
print(sgstr)
drawLSystem(t, sgstr, 120, 20)
for i in range(2):
  print(i)
  t.left(120)
  t.forward(20 * 2**4)

它应该只绘制到达右下角后剩余的外三角形的两条边。

【问题讨论】：

标签： python turtle-graphics

【解决方案1】：

您的代码清理在 repl.it 和 Python 控制台中运行良好：

from turtle import Screen, Turtle

ANGLE = 120
LENGTH = 20
ITERATIONS = 4

def SGRules(character):
    if character == 'F':
        return 'F+F-F-F+F'

    return character

def processStr(string, rules):
    new_string = ""

    for character in string:
        new_string += rules(character)

    return new_string

def createLSystem(iterations, axiom, rules):
    string = ""

    for _ in range(iterations):
        string = processStr(axiom, rules)
        axiom = string

    return string

def drawLSystem(turtle, lsys, angle, length):
    for command in lsys:
        if command == 'F':
            turtle.forward(length)
        elif command == '+':
            turtle.left(angle)
        elif command == '-':
            turtle.right(angle)

yertle = Turtle('turtle')
yertle.speed('fastest')
yertle.shape('turtle')
yertle.color('dark green', 'light green')

sg_string = createLSystem(ITERATIONS, 'F', SGRules)
print(sg_string)
drawLSystem(yertle, sg_string, ANGLE, LENGTH)

for _ in range(2):
    yertle.left(ANGLE)
    yertle.forward(LENGTH * 2 ** ITERATIONS)

screen = Screen()
screen.mainloop()

虽然我在末尾添加了对 tkinter 事件循环的传输以防止窗口关闭，但您的原始代码在 Python 控制台中运行良好。

【讨论】：