像素移动和循环Python

Question

We are using JES in my intro programming class and I have run into roadblock for my lab. The program is supposed to allow a user to select a picture and then a moth(bug) will start at the center of the picture and make random movements and change pixels to white if they are not already to simulate eating. I am stuck on the movement part. the current program below will load and eat 1 pixel at the very center but make no other movements. Could someone give me a hint as to what I am doing wrong with my random movement calls?

from random import *

def main():
 #lets the user pic a file for the bug to eat
 file= pickAFile()
 pic= makePicture(file)
 show(pic)

 #gets the height and width of the picture selected
 picHeight= getHeight(pic)
 picWidth= getWidth(pic)
 printNow("The height is: " + str(picHeight))
 printNow("The width is: " + str(picWidth))

 #sets the bug to the center of the picture
 x= picHeight/2
 y= picWidth/2
 bug= getPixelAt(pic,x,y)

 printNow(x)
 printNow(y)
 color= getColor(bug)
 r= getRed(bug)
 g= getGreen(bug)
 b= getBlue(bug)

 pixelsEaten= 0
 hungerLevel= 0


 while hungerLevel < 400 :

  if r == 255 and g == 255 and b == 255:
   hungerLevel + 1
   randx= randrange(-1,2)
   randy= randrange(-1,2)
   x= x + randx
   y= y + randy
   repaint(pic)


  else:
   setColor(bug, white)
   pixelsEaten += 1
   randx= randrange(-1,2)
   randy= randrange(-1,2)
   x= x + randx
   y= y + randy
   repaint(pic)

Answer 1

Looks like you're never updating the position of the bug within the loop. You change x and y , but this doesn't have any effect on bug .

Try:

while hungerLevel < 400 :
    bug= getPixelAt(pic,x,y)
    #rest of code goes here

---

Incidentally, if you have identical code in an if block and an else block, you can streamline things by moving the duplicates outside of the blocks entirely. Ex:

while hungerLevel < 400 :
    bug= getPixelAt(pic,x,y)
    if r == 255 and g == 255 and b == 255:
        hungerLevel + 1
    else:
        setColor(bug, white)
        pixelsEaten += 1
    randx= randrange(-1,2)
    randy= randrange(-1,2)
    x= x + randx
    y= y + randy
    repaint(pic)