两段我改过python代码，原始创意出自python programming fundamental

1. 使用turtle 画一辆卡车。这个我画得很撮。 代码如下：

def draw_truck():
    t=Turtle()
    screen=t.getscreen()

    #wheels
    t.circle(30,360)
    t.penup()
    t.forward(200)
    t.pendown()
    t.circle(30,360)
    t.penup()
    t.left(90)
    t.forward(60)
    t.right(90)
    t.forward(50)
    t.pendown()
    #draw car
    t.left(90)
    t.forward(50)
    t.left(90)
    t.forward(50)
    t.right(30)
    t.forward(50)
    t.left(30)
    t.forward(30)
    t.left(90)
    t.forward(25)
    t.right(90)
    t.forward(180)
    t.left(90)
    t.forward(50)
    t.left(90)
    t.forward(300)
    screen.exitonclick()

第二段代码： parse xml,然后使用turtle画画,原始代码是通过minidom来parse xml,我把这段代码改成了ElementTree，感觉ElementTree 要比dom 简单些，对于attributes的操作直接上字典就行了。
flowerandbg.xml 可以在这里下载：

from xml.dom import minidom
def parse_flowerandbg():
    xmldoc=minidom.parse("flowerandbg.xml")
    graphicsCommand=xmldoc.getElementsByTagName("GraphicsCommands")[0]
    commands=graphicsCommand.getElementsByTagName("Command")
    commandList=[]
    xlist=[]
    yList=[]
    widthList=[]
    colorList=[]
    radiusList=[]

    for command in commands:
        #print(command.firstChild.data.strip())
        commandList.append(command.firstChild.data.strip())
        attr=command.attributes
        if "x" in attr:
            xlist.append(attr["x"].value)
        else:
            xlist.append(None)
        if "y" in attr:
            yList.append(attr["y"].value)
        else:
            yList.append(None)

        if "width" in attr:
            widthList.append(attr["width"].value)
        else:
            widthList.append(None)
        if "color" in attr:
            colorList.append(attr["color"].value)
        else:
            colorList.append(None)

        if "radius" in attr:
            radiusList.append(attr["radius"].value)
        else:
            radiusList.append(None)

下面是我改写的代码，是用了ElementTree来parse xml文件，然后使用turtle 画画，使用turtle 画画的代码相同，故而上面的代码省略了。

import xml.etree.ElementTree
def parse_flowerandbg3():
    content=xml.etree.ElementTree.parse("flowerandbg.xml")
    root=content.getroot()
    #print (root.tag,root.attrib)
    graphiccommand=content.findall("GraphicsCommands")
    #command=content.findtext("Command")
    commands=content.findall("Command")
    commandList=[]
    xList=[]
    yList=[]
    widthList=[]
    colorList=[]
    radiusList=[]
    for command in commands:
        #print(command.tag,command.attrib,command.text)
        #print(command.text)
        commandList.append(command.text.strip())
        attr=command.attrib
        if "x" in attr:
            #print(attr["x"])
            xList.append(attr["x"])
        else:
            xList.append(None)
        if "y" in attr:
            yList.append(attr["y"])
        else:
            yList.append(None)

        if "width" in attr:
            widthList.append(attr["width"])
        else:
            widthList.append(None)
        if "color" in attr:
            colorList.append(attr["color"])
        else:
            colorList.append(None)

        if "radius" in attr:
            radiusList.append(attr["radius"])
        else:
            radiusList.append(None)

    #begin to draw
    t=turtle.Turtle()
    screen=t.getscreen()
    screen.colormode(255)
    screen.tracer(0)
    for i in range(len(commandList)):
        command=commandList[i]
        if command=="PenUp":
            t.penup()
        elif command=="PenDown":
            t.pendown()
        elif command=="GoTo":
            x=float(xList[i])
            y=float(yList[i])
            width=float(widthList[i])
            color=colorList[i]
            t.width(width)
            t.color(color)
            t.goto(x,y)
        elif command=="Circle":
            radius=float(radiusList[i])
            width=float(widthList[i])
            color=colorList[i]
            t.width(width)
            t.pencolor(color)
            t.circle(radius)
        elif command=="BeginFill":
            color=colorList[i]
            t.fillcolor(color)
            t.begin_fill()
        elif command=="EndFill":
            t.end_fill()
        else:
            print("Unknown command:",command)

    screen.update()
    screen.exitonclick()

效果如下：