As a bit of a background, I picked up a project from another developer who wrote the entire as one big file that runs from top to bottom.
The manager wants to display images / videos on the screen at certain points during the scripts execution and that disappear during other points of execution.
I have worked with Tk extensively, but I am still limited by the lack of thread safeness and its blocking mainloop() function.
Is there a way in python to display images / videos asynchronously/ in a non blocking way, while the main thread still executes? In the context of this project, the API would have to be something similar to what is below.
if __name__ == "__main__":
gui = load_gui()
gui.display_image("doing_math.png") #doesn't block
for i in range(0, 500):
print(str(i))
gui.display_image("math_complete.mp4")#doesn't block
sleep(2)
gui.clear_display()
currently I am using trying to use Tk like displayed below. but it is limited by the mainloop() blocking the rest of the scripts execution.
class MediaGui(tk.Tk):
def __init__(self):
self.mainloop()
...
gui = MediaGui() #this line blocks because of mainloop
gui.load_image("image.png")
Try this :
from concurrent.futures import ThreadPoolExecutor
gui = load_gui()
def run_io_tasks_in_parallel(tasks):
with ThreadPoolExecutor() as executor:
running_tasks = [executor.submit(task) for task in tasks]
for running_task in running_tasks:
running_task.result()
run_io_tasks_in_parallel([
lambda: gui.display_image("doing_math.png"),
lambda: gui.display_image("math_complete.mp4"),
])
Related
So I have two python threads running from inside a class. I have checked using
threading.active_count()
and it says both threads are running. The first thread includes a tkinter window which works fine. The second thread I am using as an event manager for the first window, which also works okay by itself. However, when I run the second thread alongside the first thread, the first thread does not work, ie. the window does not appear. This is even if the first thread is executed first. When I remove the infinite loop from the second thread, the first thread works again, can anyone explain this to me? Here is the class:
class Quiz(threading.Thread):
def __init__(self):
threading.Thread.__init__(self)
def show(self, question):
self.question = quiz[question][0]
self.correct = quiz[question][1]
self.incorrectA = quiz[question][2]
self.incorrectB = quiz[question][3]
self.ref = quiz[question][4]
questionDisplay.config(text=self.question)
correctButton = "answer" + str(self.ref[0])
eval(correctButton).config(text=self.correct, command=lambda : check(True))
incorrect1 = "answer" + str(self.ref[1])
eval(incorrect1).config(text=self.incorrectA, command= lambda : check(False))
incorrect2 = "answer" + str(self.ref[2])
eval(incorrect2).config(text=self.incorrectB, command= lambda : check(False))
return self.correct
def run(self):
print("thread started")
print(threading.active_count())
while True:
print(questionQueue.qsize())
if questionQueue.qsize() >= 1:
pass
else:
pass
print("looped")
Thanks
From the code as currently shown it is not obvious where the problem lies. But keep the following in mind;
Tk is event-driven like basically all GUI toolkits. So for the GUI to work you need to run Tk's mainloop. The only pieces of your code that it runs in the main loop are the various callbacks attached to things like buttons, menus and timers.
Like most GUI toolkits Tk isn't thread-safe because of the overhead that would require. To keep it working properly, you should only call Tk functions and methods from one thread.
Python's threads are operating system threads. This means they are subject to operating system scheduling. And the OS sometimes gives more time to threads that are busy. So if a thread that is spinning in a busy-loop is pre-empted (as is done regularly), chances are that it ends up being run again instead of the GUI thread.
I'm building an application that does thousands (possibly millions) of calculations based off of what the user inputs. Because these calculations can take a long time, I want to use Python's multiprocessing module. Here is my dilemma; I want to set up a tkinter window with a cancel button to stop the calculations running throughout the processors I set up using Pool. I tried using threads to allow the popup window to run, but some funny things happen when I run the code.
When I press the 'start' button, the Pool starts going as expected. However, my popup window does not show even though it is on its own thread. Even weirder, when I tell my IDE (PyCharm) to stop the program, the popup window shows and the calculations are still running until I either press the 'exit' button from the popup window, or kill the program altogether.
So my questions are: Why won't my popup window show even though it is on its own thread? Am I utilizing the multiprocessing module correctly? Or is the problem something totally different?
import tkinter as tk
from tkinter import ttk
import random
import threading
import time
from multiprocessing import Pool
def f(x):
print(x*x)
time.sleep(random.randrange(1,5)) # simulates long calculations
# Extra math stuff here...
def processor():
global calc
calc = Pool(4)
calc.map(f, [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30])
print("Done")
def calculation_start():
p = threading.Thread(target=progress_window) # Thread to open a new window for the user to cancel a calculation
p.start()
processor() # Calls the function to run the calculations
def progress_window():
# This is the window that pops up to let a user cancel a calculation.
popup = tk.Toplevel()
endButton = ttk.Button(popup, text="End", command=lambda :(calc.terminate()))
endButton.pack()
master = tk.Tk()
startButton = ttk.Button(master, text="Start", command=calculation_start)
startButton.pack()
tk.mainloop()
EDIT:
I tried switching the processor function to a thread instead of the progress_window function.
def calculation_start():
p = threading.Thread(target=processor) # Thread for the function to run the calculations
p.start()
progress_window() # Open a new window for the user to cancel a calculation
My popup window appears and the 'end' button looks like it stops the processor when pressed, but it never continues past that point. It's like it's stuck at calc.map(f, [1,2,3,...] in the processor() function.
From the Pool.map documentation:
It blocks until the result is ready.
That means that, yes, the work is being done on other threads, but the main thread (the one calling map) will not execute anything else until the other threads are complete. You want to use map_async and (for a long-running, interactive process), provide a callback for what to do when the pool is finished (probably hide the pop-up).
If you want your program to simply show the pop-up then exit, you want to use the AsyncResult returned by map_async. Set up an idle handler using after_idle (See tkinter universal widget methods and remember you'll need to manually re-add the handler after every call). After each idle call, you could call either AsyncResult.ready() or AsyncResult.get(<timeout>) to see if the pool has completed. Once it's finished, you're safe to process the results and exit.
I have a program I've been writing that began as a helper function for me to find a certain report on a shared drive based on some information in that report. I decided to give it a GUI so I can distribute it to other employees, and have ran into several errors on my first attempt to implement tkinter and threading.
I'm aware of the old adage "I had one problem, then I used threads, now I have two problems." The thread did, at least, solve the first problem -- so now on to the second....
My watered down code is:
class GetReport(threading.Thread):
def __init__(self,root):
threading.Thread.__init__(self)
# this is just a hack to get the StringVar in the new thread, HELP!
self.date = root.getvar('date')
self.store = root.getvar('store')
self.report = root.getvar('report')
# this is just a hack to get the StringVar in the new thread, HELP!
self.top = Toplevel(root)
ttk.Label(self.top,text="Fooing the Bars into Bazes").pack()
self.top.withdraw()
def run(self):
self.top.deiconify()
# a function call that takes a long time
self.top.destroy() #this crashes the program
def main():
root = Tk()
date,store,report = StringVar(),StringVar(),StringVar()
#####
## labels and Entries go here that define and modify those StringVar
#####
def launchThread(rpt):
report.set(rpt)
# this is just a hack to get the StringVar in the new thread, HELP!
root.setvar('date',date.get())
root.setvar('store',store.get())
root.setvar('report',report.get())
# this is just a hack to get the StringVar in the new thread, HELP!
reportgetter = GetReport(root)
reportgetter.start()
ttk.Button(root,text="Lottery Summary",
command=lambda: launchThread('L')).grid(row=1,column=3)
root.mainloop()
My expected output is for root to open and populate with Labels, Entries, and Buttons (some of which are hidden in this example). Each button will pull data from the Entries and send them to the launchThread function, which will create a new thread to perform the foos and the bars needed to grab the paperwork I need.
That thread will launch a Toplevel basically just informing the user that it's working on it. When it's done, the Toplevel will close and the paperwork I requested will open (I'm using ShellExecute to open a .pdf) while the Thread exits (since it exits its run function)
What's ACTUALLY happening is that the thread will launch its Toplevel, the paperwork will open, then Python will become non-responsive and need to be "end processed".
As far as I know you cannot use Threading to alter any GUI elements. Such as destroying a Toplevel window.
Any Tkinter code needs to be done in the main loop of your program.
Tkinter cannot accept any commands from threads other than the main thread, so launching a TopLevel in a thread will fail by design since it cannot access the Tk in the other thread. To get around this, use the .is_alive method of threads.
def GetReport(threading.Thread):
def __init__(self,text):
self.text = text
super().__init__()
def run(self):
# do some stuff that takes a long time
# to the text you're given as input
def main():
root = Tk()
text = StringVar()
def callbackFunc(text):
top = Toplevel(root)
ttk.Label(top,text="I'm working here!").pack()
thread = GetReport(text)
thread.start()
while thread.is_alive():
root.update() # this keeps the GUI updating
top.destroy() # only when thread dies.
e_text = ttk.Entry(root,textvariable=text).pack()
ttk.Button(root,text="Frobnicate!",
command = lambda: callbackFunc(text.get())).pack()
okay so now i am almost finished with my little project with some bits left, that's running my background task and then showing my GUI.
class myGUIApp:
def __init()__:
....
def createwidgets():
....
if __name__ == "__main__":
import myBackgroundTasks
x = myBackgroundTasks()
x.startbackground1() <----- this is background task that doesn't need user interaction
x.startbackground2() <----- this is background task that doesn't need user interaction
MainWindow = myGUIApp()
MainWindow.show() <---- this is Pyside GUI
The issue is this, the GUI doesn't "show" until my 2 background tasks are finished, which can take quite some time as they are doing I/O jobs and grabber files from the internet. How should i go about this? Using python's multithread (inside the background task, i am also using multithreading)? Qthread? or multiprocessing module? or others? thanks for answering.
You could put it on a thread. Since the Qt gui runs in its own thread this is efficient use. Use a queue to pass back the results of x. The only trick is where and when do you need x? If you need it inside your gui then the best thing to do is use the gui's after method, if it has one, or whatever it's equivalent is. The point is you don't hog up all the resources continuously checking the queue for the output. If you put a while loop inside your gui, it will probably cause the gui to freeze.
from threading import Thread
from Queue import Queue
class myGUIApp:
def __init()__:
....
def createwidgets():
....
if __name__ == "__main__":
import myBackgroundTasks
QUEUE = Queue()
def queue_fun(q):
x = myBackgroundTasks()
x.startbackground1() <----- this is background task that doesn't need user interaction
x.startbackground2() <----- this is background task that doesn't need user interaction
q.put(x)
THREAD = Thread(target=queue_fun, args=QUEUE)
THREAD.start()
MainWindow = myGUIApp()
MainWindow.show() <---- this is Pyside GUI
# if you can wait until after mainloop terminates to get x, put this here
while THREAD.is_alive()
try:
x = QUEUE.get_nowait()
except Queue.Empty:
continue
# if you need this inside Pyside, then you should put this inside Pyside,
# but don't use while loop, use Qt after function and call self.wait
def wait(self):
try:
x = QUEUE.get_nowait()
except Queue.Empty:
self.after(5, self.wait)
I have written a short module that can be passed an image and simply creates a Tkinter window and displays it. The problem that I am having is that even when I instantiate and call the method that displays the image in a separate thread, the main program will not continue until the Tkinter window is closed.
Here is my module:
import Image, ImageTk
import Tkinter
class Viewer(Tkinter.Tk):
def __init__(self,parent):
Tkinter.Tk.__init__(self,parent)
self.parent = parent
self.initialize()
def initialize(self):
self.grid()
def show(self,img):
self.to_display = ImageTk.PhotoImage(img)
self.label_image = Tkinter.Label(self,image=self.to_display)
self.label_image.grid(column = 0, row = 0, sticky = "NSEW")
self.mainloop()
It seems to work fine, except when I call it from my test program like the one below, it will not seem to allow my test program to continue, even when started in a different thread.
import Image
from viewer import Viewer
import threading
def showimage(im):
view = Viewer(None)
view.show(im)
if __name__ == "__main__":
im = Image.open("gaben.jpg")
t = threading.Thread(showimage(im))
t.start()
print "Program keeps going..."
I think that perhaps my problem is that I should be creating a new thread within the module itself, but I was wanting to just try and keep it simple, as I am new to Python.
Anyway, thanks in advance for any assistance.
edit: To clarity, I am just trying to make a module that will display an image in a Tkinter window, so that I can use this module any time I want to display an image. The problem that I am having is that any time a program uses this module, it cannot resume until the Tkinter window is closed.
Tkinter isn't thread safe, and the general consensus is that Tkinter doesn't work in a non-main thread. If you rewrite your code so that Tkinter runs in the main thread, you can have your workers run in other threads.
The main caveat is that the workers cannot interact with the Tkinter widgets. They will have to write data to a queue, and your main GUI thread will have to poll that queue.
If all you're doing is showing images, you probably don't need threading at all. Threading is only useful when you have a long running process that would otherwise block the GUI. Tkinter can easily handle hundreds of images and windows without breaking a sweat.
From your comments it sound's like you do not need a GUI at all. Just write the image to disk and call an external viewer.
On most systems it should be possible to launch the default viewer using something like this:
import subprocess
subprocess.Popen("yourimage.png")
From what I can tell, Tkinter doesn't like playing in other threads. See this post...I Need a little help with Python, Tkinter and threading
The work around is to create a (possibly hidden) toplevel in your main thread, spawn a separate thread to open images, etc - and use a shared queue to send messages back to the Tk thread.
Are you required to use Tkinter for your project? I like Tkinter. It's "quick and dirty." - but there are (many) cases where other GUI kits are the way to go.
I have tried to run tkinter from a separate thread, not a good idea, it freezes.
There is one solution that worked. Run the gui in the main thread, and send events to the main gui. This is similar example, it just shows a label.
import Tkinter as t
global root;
root = t.Tk()
root.title("Control center")
root.mainloop()
def new_window(*args):
global root
print "new window"
window = t.Toplevel(root)
label = t.Label(window, text="my new window")
label.pack(side="top", fill="both", padx=10, pady=10)
window.mainloop()
root.bind("<<newwin>>",new_window)
#this can be run in another thread
root.event_generate("<<newwin>>",when="tail")