Tkinter window freezes even if threading is used

Question

I'm making an Python program which downloads files. I use Tkinter as GUI, but it freezes while it's downloading larger files which stops buffer from showing. I tried to use threading, as it's suggested in similar questions on SO but nothing changed. Here's code:

labelText1 = StringVar()
labelText1.set("Double-click file to download...")
label11 = Label(app, textvariable=labelText1, height=2, bg="#DF1A2B", fg="white")
label11.place(x=50, y=50)

def download_file(url):
    file_name = url.split('/')[-1]
    u = urllib2.urlopen(url)
    f = open("./downloads/" + file_name, 'wb')
    meta = u.info()
    file_size = int(meta.getheaders("Content-Length")[0])
    print "Downloading: %s" % (file_name)
    os.system('cls')
    file_size_dl = 0
    block_sz = 8192
    while True:
        buffer = u.read(block_sz)
        if not buffer:
           break

        file_size_dl += len(buffer)
        f.write(buffer)
        status = r"%10d  [%3.2f%%]" % (file_size_dl, file_size_dl * 100. / file_size)
        status = status + chr(8)*(len(status)+1)
        labelText1.set(status,)
        tuple = (file_name, status)
    f.close()
    onEnd()

def onEnd():
    labelText1.set("Status: done!")

def double_clicked(clicked):
    tuple = mlb.get(clicked)[0]
    url = str(tuple[2])
    if tuple[1] != "Folder":
       t = threading.Thread(target=download_file(url))
       t.start()
    else:
        print "FOLDER HANDLING GOES HERE"

Is there any other way which will allow me to change label text while download process is still running?

Answer 1

Just because it's in a separate thread the GUI can still "hang" if it has a long section of code in it (eg your while loop). Add a GUI refresh during the while loop so that it gets a chance to redraw, eg using update() .