Tkinter managing my event loops alongside my mainloop

Question

I\'ve been slowly learning Tkinter and object-oriented programming but I\'ve programmed myself into a corner with this one. please forgive my lack of critical thinking on th

Answer 1

You are looking for threading. Put the event you want to run in another thread. See this example:

import thread, time
def myfunc(a1,a2):
    while True:
      print a1,a2
      time.sleep(1)
thread.start_new_thread(myfunc,("test","arg2")
tkroot.mainloop()

Now you have a function running along with the Tkinter window that prints the args every second.

EDIT: I don't know why so many down votes. Tkinter DOES work well with threads, I've already used this trick several times without problems. See this example:

Download a 10 MB file and log the progress to a Tkinter window.

Without threading:

import urllib2,thread
import Tkinter as tk

class Example(tk.Frame):
    def __init__(self, parent):
        tk.Frame.__init__(self, parent)   

        self.parent = parent        
        self.initUI()

    def initUI(self):

        self.pack(fill=tk.BOTH, expand=1)

        canvas = tk.Canvas(self)

        self.text = canvas.create_text(18,18,anchor=tk.W,font="Purisa",text="Status: Press start to download...")
        but=tk.Button(text="Start",command=self.start)
        canvas.create_window((270,18),window=but)

        canvas.pack(fill=tk.BOTH, expand=1)
        self.canvas=canvas

    def start(self):
        #thread.start_new_thread(
        self.download("http://ipv4.download.thinkbroadband.com/10MB.zip","10mb.zip")
        #)

    def onEnd(self):
            self.canvas.itemconfig(self.text, text="Status: done!")

    def download(self,url,file_name):
        u = urllib2.urlopen(url) 
        f = open(file_name, 'wb')
        meta = u.info()
        file_size = int(meta.getheaders("Content-Length")[0])
        print "Downloading: %s Bytes: %s" % (file_name, file_size)

        file_size_dl = 0
        block_sz = 1024*50 #50 kb
        while True:
            buffer = u.read(block_sz)
            if not buffer:
                break

            file_size_dl += len(buffer)
            f.write(buffer)
            status = r"[%3.2f%%]" % (file_size_dl * 100. / file_size)
            self.canvas.itemconfig(self.text,text="Status: downloading..."+status)

        f.close()

        self.onEnd()

def main():
    root = tk.Tk()
    root.resizable(0,0)
    ex = Example(root)
    root.geometry("300x70")
    root.mainloop()  

main()

The window freezes till the download is done.

With thread:

import urllib2,thread
import Tkinter as tk

class Example(tk.Frame):
    def __init__(self, parent):
        tk.Frame.__init__(self, parent)   

        self.parent = parent        
        self.initUI()

    def initUI(self):

        self.pack(fill=tk.BOTH, expand=1)

        canvas = tk.Canvas(self)

        self.text = canvas.create_text(18,18,anchor=tk.W,font="Purisa",text="Status: Press start to download...")
        but=tk.Button(text="Start",command=self.start)
        canvas.create_window((270,18),window=but)

        canvas.pack(fill=tk.BOTH, expand=1)
        self.canvas=canvas

    def start(self):
        thread.start_new_thread(
        self.download("http://ipv4.download.thinkbroadband.com/10MB.zip","10mb.zip")
        )

    def onEnd(self):
            self.canvas.itemconfig(self.text, text="Status: done!")

    def download(self,url,file_name):
        u = urllib2.urlopen(url) 
        f = open(file_name, 'wb')
        meta = u.info()
        file_size = int(meta.getheaders("Content-Length")[0])
        print "Downloading: %s Bytes: %s" % (file_name, file_size)

        file_size_dl = 0
        block_sz = 1024*50 #50 kb
        while True:
            buffer = u.read(block_sz)
            if not buffer:
                break

            file_size_dl += len(buffer)
            f.write(buffer)
            status = r"[%3.2f%%]" % (file_size_dl * 100. / file_size)
            self.canvas.itemconfig(self.text,text="Status: downloading..."+status)

        f.close()

        self.onEnd()

def main():
    root = tk.Tk()
    root.resizable(0,0)
    ex = Example(root)
    root.geometry("300x70")
    root.mainloop()  

main()

Doesn't freeze and the text is updated normally.

Answer 2

You already have an infinite loop running, so you shouldn't be trying to add another one. Instead, you can use the after method to cause a function to be repeatedly called every so often. In your case, you can replace this:

def updateStock(self):
   while True:
        labelName = str(s) + "Label"
        stockPrice = get_quote(s)
        self.labelName = Label(self.myContainer1, text = s.upper() + ": " + str(stockPrice))
        self.labelName.pack()
        time.sleep(10)

... with this:

def updateStock(self):
    labelName = str(s) + "Label"
    stockPrice = get_quote()
    self.labelName = Label(self.myContainer1, text = s.upper() + ": " + str(stockPrice))
    self.labelName.pack()
    self.after(10000, self.updateStock)

This will get a quote, add a label, then arrange for itself to be called again in 10 seconds (10,000 ms).

However, I doubt that you want to create a new label every 10 seconds, do you? Eventually the window will fill up with labels. Instead, you can create a label once, then update the label in each iteration. For example, create self.label once in the init, then in the loop you can do:

self.labelName.configure(text=s.upper() + ": " + str(stockPrice))