I'm running a slowish process of building a set of PDFs using LaTeX that's put together by my script.
The PDFs are built in a for loop. I wanted to show a status window that would add a line for each student that the loop goes through, so that you could see the progress. I have been doing this with print, but I wanted something that integrated well with the Tkinter interface that I have moved to.
I have this:
ReStatuswin = Toplevel(takefocus=True)
ReStatuswin.geometry('800x300')
ReStatuswin.title("Creating Reassessments...")
Rebox2 = MultiListbox(ReStatuswin, (("Student", 15), ("Standard", 25), ("Problems", 25) ))
Rebox2.pack(side = TOP)
OKR = Button(ReStatuswin, text='OK', command=lambda:ReStatuswin.destroy())
OKR.pack(side = BOTTOM)
and then the loop:
for row in todaylist:
and then, inside the loop, after the PDF has been made,
Rebox2.insert(END, listy)
It inserts the row fine, but they all show up (along with the ReBox2 window itself) only after the entire loop is finished.
Any idea about what's causing the delay in display?
Thanks!
Yes, from what I can tell, there are two problems. First, you are not updating the display with each new entry. Second, you are not triggering the for loop with a button but instead having it run on startup (which means that the display won't be created until after the loop exits). Unfortunately however, I can't really work with the code you gave because it is a snippet of a much larger thing. However, I made a little script that should demonstrate how to do what you want:
from Tkinter import Button, END, Listbox, Tk
from time import sleep
root = Tk()
# My version of Tkinter doesn't have a MultiListbox
# So, I use its closest alternative, a regular Listbox
listbox = Listbox(root)
listbox.pack()
def start():
"""This is where your loop would go"""
for i in xrange(100):
# The sleeping here represents a time consuming process
# such as making a PDF
sleep(2)
listbox.insert(END, i)
# You must update the listbox after each entry
listbox.update()
# You must create a button to call a function that will start the loop
# Otherwise, the display won't appear until after the loop exits
Button(root, text="Start", command=start).pack()
root.mainloop()
Related
I've been learning python for a month now and run into my first brick wall. I have a large art viewer GUI program and at one point want to put an image on screen with a countdown counter-approx every 5 secs. I thought of a code such as the one below The problem is that this uses update and all my reading says that update is bad (starts a new event loop (?)) and that I should use update_idletasks. when I replace update with update_idletasks in the code below the countdown button is not visible until it reaches single figures, update superficially works fine. But also the q bound key calls the subroutine but has no effect
from tkinter import *
import sys
import time
root = Tk()
def q_key(event):
sys.exit()
frame=Frame(root, padx=100, pady=100, bd=10, relief=FLAT)
frame.pack()
button=Button(frame,relief="flat",bg="grey",fg="white",font="-size 18",text="60")
button.pack()
root.bind("q",q_key)
for x in range(30, -1, -5) :
button.configure(text=str(x))
button.update()
print(x)
button.after(5000)
root.mainloop()
In this case you don't need update nor update_idletasks. You also don't need the loop, because tkinter is already running in a loop: mainloop.
Instead, move the body of the loop to a function, and call the function via after. What happens is that you do whatever work you want to do, and then schedule your function to run again after a delay. Since your function exits, tkinter returns to the event loop and is able to process events as normal. When the delay is up, tkinter calls your function and the whole process starts over again.
It looks something like this:
def show(x):
button.configure(text=x)
if x > 0:
button.after(5000, show, x-5)
show(30)
I would like to understand why this code:
import time
for i in range(1,11):
print(i)
time.sleep(1)
shows (as it should!) numbers from 1 to 10, each every 1 second, while this code:
from tkinter import *
import time
root = Tk()
for i in range(1,11):
Label(root, text = i).grid(row=0, column=i-1, padx=5, pady =5)
time.sleep(1)
root.mainloop()
waits for 10 seconds, and then displays a window with the 10 numbers (instead of adding them one by one).
I am aware this is a silly question, but I really can't understand! Many Thanks! Alessandro
Most GUI's work differently to what you expect.
They work in an asynchronous way, which means, that you setup your windows and start an event loop.
This event loop will display all widgets, labels, etc, that you set up before calling the event loop and wait for any events (GUI events like mouse or keyboard events, timer events and perhaps network events).
When any event is encountered code associated to that event will be called and this code can request to change the GUI (show or hide elements, change labels or attributes of graphical widgets) However the change to the GUI will only be performed when you give control back to the event loop (when the code handling an event finished)
In your given code you change a label in a for loop with sleep statements, but only after the for loop is finished your main loop is being called and this is the moment, where the final state of your GUI will be displayed.
So what you encounter is a know issue for almost all GUI / asynhronous kind of applications.
You have to rewrite your code such, that you start a timer event, and when the timer event fires a function will set a label and increase the counter by 1. And if the counter is not 11 it will restart another timer
This is because the time.sleep function is before the root.mainloop function.
root.mainloop is what causes the window to appear on-screen and start doing things. Instead, I'd recommend using window.after, as that tells the window to run a function after some time when it's on-screen.
Here's an example of a modification you could make (it's not that good but it works):
from tkinter import *
import time
root = Tk()
progress = 0
end = 10
def update_progress():
global progress
progress += 1
Label(root, text = progress).grid(row=0, column=progress-1, padx=5, pady =5)
if progress < end: root.after(1000,update_progress) # Tell the window to call this function in 1000ms (1 second)
root.after(0,update_progress) # Tell the window to run the update_progress function 0ms after now.
root.mainloop()
I'd recommend looking at gelonida's answer for an explanation of why your original code didn't work, and what you need to keep in mind when programming with GUIs in the future.
I was racking my brain a bit trying to figure out why a tkinter window would only appear after I had stopped my script. Turns out, it won't appear if the delay time in my root.after (that is within my infinite fruity loop) was set to 0. Setting it to 1 or higher caused it to work correctly. Is this a bug or am I missing something important about how .after works? I'm running this with Python 2.7 in Anaconda on mac OS.
import time
import Tkinter as tk
import random
root = tk.Tk()
root.title("random numbers")
root.geometry("220x220+5+5")
frame = tk.Frame(root, width=210, height=210)
frame.pack()
luckynumber = tk.IntVar()
label1 = tk.Label(frame, text="random number").pack(side=tk.LEFT)
display1 = tk.Label(frame, textvariable=luckynumber)
display1.pack( side=tk.LEFT )
def askrandy():
randy = random.randrange(0, 100, 1)
luckynumber.set(randy)
def fruityloop():
time.sleep(.5)
askrandy()
root.after(1, fruityloop)
root.after(0, fruityloop)
root.mainloop()
Second question: this code doesn't run very smoothly. Seeing as it's quite simple, I assumed it would be pretty solid. But I find that it takes a couple seconds to get started and moving the window around causes it to stutter as well. Would this work better with my main loop run as a class?
This is normal behavior.
Tkinter maintains a queue of work to be done when it goes idle. This is the "idle" queue.
When you call after, the function you supply is added to this queue. When the main event loop (or a call to after_idle) processes the queue, it looks for items on the queue that should be run based on the current time and the time that the item should be run. All items that are due to be run are run before processing of the queue stops.
If one of those adds an item to the queue with a value of zero it will be run since its time is due. If that item itself adds an item to the queue, then you take one item off of the queue and immediately put one one so the queue will never become empty. If the queue never becomes empty, tkinter isn't able to process other types of events.
The reason that the program seems slow and jerky is because of the call to sleep. When you call sleep, tkinter does exactly that: it sleeps. It cannot process any events, even events that simply refresh the window. If you want askrandy to be called once every half second, you should simply call after with a value of 500, rather than call it with a value of zero and then sleep for half a second.
Whether the main window is a class or not will not affect your program all all. You simply need to stop using sleep, and provide sane values to after. If you are trying to show a simple animation, a value of 30 is about as small as you need to go.
This is how it should looks without sleep(). But I don't know if it can help. It works fast on Linux.
If you run code in IDLE then you may have problem because it uses Tkinter to display windows and runs own mainloop() but Tkinter should run only one mainloop(). You can try directly in console python script.py.
import Tkinter as tk
import random
# --- functions ---
def fruityloop():
randy = random.randrange(0, 100, 1)
luckynumber.set(randy)
# run again after 500ms = 0.5s
root.after(500, fruityloop)
# --- main ---
root = tk.Tk()
root.title("random numbers")
root.geometry("220x220+5+5")
luckynumber = tk.IntVar()
frame = tk.Frame(root, width=210, height=210)
frame.pack()
label = tk.Label(frame, text="random number")
label.pack(side=tk.LEFT)
display = tk.Label(frame, textvariable=luckynumber)
display.pack(side=tk.LEFT)
# run first time
fruityloop()
root.mainloop()
I am working on a large program that opens new windows from a desktop widget. The desktop widget has a 'ticker' style label that displays a piece of text representing an iteration through a list. My problem is when I first wrote the program I called mainloop() with each new window I opened. The result was the new window and program would run as designed, but the ticker would freeze. Even upon closing the newly created window, the ticker would not restart. So I removed the mainloop() line. The result of this is the ticker continues to run and I can work within the new window, but everything is soooo laggy. I suspect this has something to do with the after() method?
Attached is a test code that I am using to try to sort this out before applying the correct code to my program. And I'm sure you can tell by reading the code, but I am self taught and an absolute newb, so please dumb down the explanations if possible. Thank so much!
from tkinter import *
def new_window():
nw = Tk()
item = Text(nw)
item.grid()
L = [1, 2, 3, 4, 5]
root = Tk()
Button(root, text = 'Open', command = new_window).grid(row = 1)
while True:
for i in L:
num = Label(root, text = i)
num.grid(row = 0)
root.after(2500)
num.update()
root.mainloop()
A tkinter application should always have exactly one instance ofTk, and you should call mainloop exactly once. If you have more than one instance the program will not likely work the way you expect. It's possible to make it work, but unless you understand exactly what is happening under the hood you should stick to this rule of thumb.
If you need more windows, create instances of Toplevel. You should not call mainloop for each extra window.
Also, you shouldn't have an infinite loop where you call after the way that you do. mainloop is already an infinite loop, you don't need another. There are several examples on this website of using after to call a function at regular intervals without creating a separate loop.
Hi
so first of all i made a program that downloads music and displays the percent that has downloaded in a list box.
kind of like this
from Tkinter import *
from urllib2 import *
admin = Tk()
Admin = Tk()
listbox = Listbox(admin, bg="PURPLE")
listbox.pack()
def fores():
chunks = 10000
dat = ''
song = '3 rounds and a sound'
url = 'http://bonton.sweetdarkness.net/music/Blind%20Pilot%20--%203%20Rounds%20and%20A%20Sound.mp3'
down = urlopen(url)
downso = 0
tota = down.info().getheader('Content-Length').strip()
tota = int(tota)
while 1:
a = down.read(chunks)
downso += len(a)
if not a:
break
dat += a
percent = float(downso) / tota
percent = round(percent*100, 1)
listbox.insert(END, percent)
listbox.update()
listbox.delete(0, END)
listbox.insert(END, percent)
listbox.update()
button = Button(Admin, text='Download', command=fores)
button.pack()
button = Button(Admin, text='Download', command=fores)
button.pack()
mainloop()
I wont show you the original program for it is over the limit of the post size.
On my original program if i move the window before i download an mp3 file it downloads less then 3 % and stops and if i then close the window it starts downloading again.
does anyone know why this is or if there is an alternative to displaying the percentage on the Tkinter window?
Please help
and update_idletasks doesent work
The proper widget for displaying a string is a Label. You can change the text at runtime with the configure method:
self.progress = Label(...)
...
self.progress.configure(text="%s%% completed" % percent)
Second, you are creating two root windows - admin and Admin. And strangely, you are putting the listbox in one and the buttons in another. Tk isn't designed to work like that. Third, you need to call the mainloop method of your (single) root window (eg: Admin.mainloop)
Finally, as to your comment that update_idletasks doesn't work -- please define "doesn't work". It will in fact update the display. What it won't do is let you interact with the window while it is running.
I made changes to your code based on the above comments (created only one root, used a Label rather than Listbox, and used update_idletasks and the program ran to completion, downloading the song.
The danger of calling update is this: what if you click the "download" button while you are already downloading? What happens is the next time update is called, that button press will be serviced. In the servicing of that event you'll enter an infinite loop. While that inner infinite loop is running the outer one cannot run. You will have effectively frozen the first download.
The proper solution involves one of (at least) two techniques. One, create a thread to do the downloading, and have it periodically send information back to the main loop so it can update the progress bar. The second is to leverage the already existing infinite loop -- the event loop -- and do your reading of chunks one at a time by placing jobs on the event queue with after.
There are examples on the internet for both approaches.
i use a ttk.Progressbar, all you have to do is associate a variable to it and update that particular variable.
http://docs.python.org/library/ttk.html#progressbar
http://www.tkdocs.com/tutorial/morewidgets.html#progressbar