Python 2.X / Tkinter需要打印才能运行

Question

Firstly, very much Py Newby! I have written a program to import data from a file and display it as an image using tkinter. The loop that is misbehaving runs thus:

Get data and plot

for x in xrange(WIDE):
    for y in xrange(HIGH):
        dataPointLo = inFile.read(1)
        dataPointHi = inFile.read(1)
        pixelValue = ((ord(dataPointLo) + 256*(ord(dataPointHi)))-31500)
        colour = rgb[pixelValue]
        #print below makes prog run!
        print pixelValue
        img.put(colour, to=(x,y))

As suggested by the comment, leaving out the print stops it working, but it locks one core of the processor at 100% for as long as you leave it (well at least 20 mins!). This effect occurs both in IDLE and from the command line (Ubuntu 12.04). Of course, the print to the IDLE window slows the program down, so I would like to remove it! Any thoughts?

Answer 1

it sounds like the process you are running takes a long time to complete, i would suggest that the reason you think it stops is because the window doesn't update while the process is busy unless you tell it to. i suggest you add a function like the following to your code and call it once before you enter your loop:

def keep_alive(self):
    self.update()
    self.after(100, self.keep_alive)

this way you are adding an event to update the window every 100ms(ish) to the event loop, which will keep the program responsive. you can adjust the timing to suit you, too often will slow your loop down, too far apart and the program will feel sluggish.