Python turtle绘制行星时定义画笔颜色后画笔仍未变色问题

问题原因 #

颜色不生效本质是阴影绘制循环根本没有执行，结合代码里的其他错误，具体问题如下：

• 循环判断条件逻辑错误：arc初始值为70，编写的循环条件while arc < 45永远不成立，循环体完全不会运行，自然看不到新颜色的绘制效果
• 方法名拼写错误：循环内的pen.cirlce是错误写法，正确为pen.circle，执行到此处会直接抛出异常终止运行
• 循环终止逻辑不匹配：循环内每次执行arc -= 2，对应正确的循环条件应为while arc > 45，初始值70每次减2，降到45以下时停止，符合弧段绘制的设计逻辑

修正后代码 #

from turtle import Screen, Pen
import turtle
import random
plansize = random.randrange(1, 5)


screen = Screen()
screen.title("Planet test")
pen = Pen()
pen.speed(0)
pen.pensize(3)
pen.hideturtle()
turtle.bgcolor('black')
plasizetrue = plansize*50
screen.colormode(255)

def placreate():
    arc = 70
    randomr = int(random.randrange(0,255))
    randomg = int(random.randrange(0,255))
    randomb = int(random.randrange(0,255))
    pen.pencolor(randomr, randomg, randomb)
    counter = 0
    plasizetrue = plansize*100
    pen.right(90)
    pen.circle(plasizetrue)
    while plasizetrue > 0:
        plasizetrue -= 1
        pen.circle(plasizetrue)
        counter += 1
    # 用min简化边界判断，减少冗余代码
    randomr = min(randomr + 50, 255)
    randomg = min(randomg + 50, 255)
    randomb = min(randomb + 50, 255)
    pen.pencolor(randomr, randomg, randomb)
    # 修正循环条件
    while arc > 45:
        pen.circle(counter, -arc)
        pen.left(87)
        pen.forward(3)
        pen.right(87)
        arc -= 2
        # 修正拼写错误
        pen.circle(counter, arc)
        pen.right(87)
        pen.forward(3)
        pen.right(87)

placreate()
turtle.done()

内容的提问来源于stack exchange，提问作者Zeploin