Me and a friend are having a programming challenge to who can make a good VOS (Virtual Operating System) and currently mine is running custom programs from Threads within the program, I am using Tkinter currently so the separate Threads have their own self.master.mainloop(). I have all the Threads stored in a list but I was wondering whether I could call a function in the Thread which would call a subroutine in the program telling it to do self.master.destroy(). Is there any way to do this?
I would like something along the lines of
class ToBeThread():
def __init__(self):
self.master = Tk()
self.master.mainloop()
def on_stop(self, reason):
self.master.destroy()
Then in my main class
from threading import Thread
thread = Thread(ToBeThread())
thread.setDaemon(True)
thread.on_stop += ToBeThread.on_stop # Similar to how it is done in c#
thread.start()
...
...
thread.stop() # This calls the functions related to the "on_stop"
I have found a way to do this, so for any wondering I did:
from threading import Thread
class MyThread(Thread):def __init__(self, method, delay=-1):
Thread.__init__(self)
self.method = method
self._running = False
self.delay = delay
self.setDaemon(True)
def run(self):
self._running = True
while self._running == True:
self.method()
if self.delay != -1:
time.sleep(self.delay)
def stop(self):
self._running = False
This allows me to write pass a function in through the initialiser, and it will run it ever x seconds or as many times as possible until I do thread.stop()
Related
I am currently trying to implement some threading functionality in my PySide6 GUI application. I followed a tutorial to try to get started (link is here), and I cannot seem to get it to work. Although that tutorial uses PyQt not PySide, the classes and structure is still similar, and it does seem to launch on another thread. Still though, it freezes the main GUI, which is not desired when this actually faces users.
Here is a sample of my code:
class Worker(QObject):
finished = Signal(str)
progress = Signal(int)
def run(self, file):
"""Long-running task." that calls a separate class for computation""
b = SeparateClass()
b.doComputation()
self.finished.emit()
class DataPlotting(QMainWindow):
def __init__(self):
self.thread = QThread()
self.worker = Worker()
self.report_builder = QPushButton('Call class that threads')
self.report_builder.setEnabled(False)
self.report_builder.clicked.connect(self.qthread_test)
def qthread_test(self):
file = 'some_file.txt'
self.worker.moveToThread(self.thread)
self.thread.started.connect(self.worker.run(file))
self.worker.finished.connect(self.thread.quit)
self.worker.finished.connect(self.worker.deleteLater)
self.thread.finished.connect(self.thread.deleteLater)
self.thread.start()
return
This does accomplish the work that is in the Worker class and spit out the desired results, but it freezes the GUI. I am not really sure what I am doing wrong, as this approach is what has been suggested to prevent freezing GUIs for heavy computation.
Is there something that I am straight up missing? Or am I going about this the wrong way? Any help or guidance is appreciated
I am assuming that you make the appropriate calls to the super class during __init__ for your subclasses of QMainWindow and the QObject.
When your code executes self.thread.started.connect(self.worker.run(file)) that line it runs the function self.worker.run(file) immediately and assigns the result of that function, which is None, as the connected slot to the thread.started signal. Instead of passing the file path as a parameter you can assign it to the worker instance and have the run method grab the path from self during execution.
For example you can try something like this:
class Worker(QObject):
finished = Signal(str)
progress = Signal(int)
def run(self):
"""Long-running task." that calls a separate class for computation"""
file = self.some_file
b = SeparateClass()
b.doComputation()
self.finished.emit()
class DataPlotting(QMainWindow):
def __init__(self):
self.report_builder = QPushButton('Call class that threads')
self.report_builder.setEnabled(False)
self.report_builder.clicked.connect(self.qthread_test)
self.threads = []
def qthread_test(self):
worker = Worker()
thread = QThread()
worker.some_file = 'some_file.txt'
worker.moveToThread(thread)
thread.started.connect(worker.run)
worker.finished.connect(thread.quit)
worker.finished.connect(worker.deleteLater)
thread.finished.connect(thread.deleteLater)
thread.start()
self.threads.append(thread)
return
There is a solution posted here to create a stoppable thread. However, I am having some problems understanding how to implement this solution.
Using the code...
import threading
class StoppableThread(threading.Thread):
"""Thread class with a stop() method. The thread itself has to check
regularly for the stopped() condition."""
def __init__(self):
super(StoppableThread, self).__init__()
self._stop_event = threading.Event()
def stop(self):
self._stop_event.set()
def stopped(self):
return self._stop_event.is_set()
How can I create a thread that runs a function that prints "Hello" to the terminal every 1 second. After 5 seconds I use the .stop() to stop the looping function/thread.
Again I am having troubles understanding how to implement this stopping solution, here is what I have so far.
import threading
import time
class StoppableThread(threading.Thread):
"""Thread class with a stop() method. The thread itself has to check
regularly for the stopped() condition."""
def __init__(self):
super(StoppableThread, self).__init__()
self._stop_event = threading.Event()
def stop(self):
self._stop_event.set()
def stopped(self):
return self._stop_event.is_set()
def funct():
while not testthread.stopped():
time.sleep(1)
print("Hello")
testthread = StoppableThread()
testthread.start()
time.sleep(5)
testthread.stop()
Code above creates the thread testthread which can be stopped by the testthread.stop() command. From what I understand this is just creating an empty thread... Is there a way I can create a thread that runs funct() and the thread will end when I use .stop(). Basically I do not know how to implement the StoppableThread class to run the funct() function as a thread.
Example of a regular threaded function...
import threading
import time
def example():
x = 0
while x < 5:
time.sleep(1)
print("Hello")
x = x + 1
t = threading.Thread(target=example)
t.start()
t.join()
#example of a regular threaded function.
There are a couple of problems with how you are using the code in your original example. First of all, you are not passing any constructor arguments to the base constructor. This is a problem because, as you can see in the plain-Thread example, constructor arguments are often necessary. You should rewrite StoppableThread.__init__ as follows:
def __init__(self, *args, **kwargs):
super().__init__(*args, **kwargs)
self._stop_event = threading.Event()
Since you are using Python 3, you do not need to provide arguments to super. Now you can do
testthread = StoppableThread(target=funct)
This is still not an optimal solution, because funct uses an external variable, testthread to stop itself. While this is OK-ish for a tiny example like yours, using global variables like that normally causes a huge maintenance burden and you don't want to do it. A much better solution would be to extend the generic StoppableThread class for your particular task, so you can access self properly:
class MyTask(StoppableThread):
def run(self):
while not self.stopped():
time.sleep(1)
print("Hello")
testthread = MyTask()
testthread.start()
time.sleep(5)
testthread.stop()
If you absolutely do not want to extend StoppableThread, you can use the current_thread function in your task in preference to reading a global variable:
def funct():
while not current_thread().stopped():
time.sleep(1)
print("Hello")
testthread = StoppableThread(target=funct)
testthread.start()
sleep(5)
testthread.stop()
I found some implementation of a stoppable thread - and it does not rely that You check if it should continue to run inside the thread - it "injects" an exception into the wrapped function - that will work as long as You dont do something like :
while True:
try:
do something
except:
pass
definitely worth looking at !
see : https://github.com/kata198/func_timeout
maybe I will extend my wrapt_timeout_decorator with such kind of mechanism, which You can find here : https://github.com/bitranox/wrapt_timeout_decorator
Inspired by above solution I created a small library, ants, for this problem.
Example
from ants import worker
#worker
def do_stuff():
...
thread code
...
do_stuff.start()
...
do_stuff.stop()
In above example do_stuff will run in a separate thread being called in a while 1: loop
You can also have triggering events , e.g. in above replace do_stuff.start() with do_stuff.start(lambda: time.sleep(5)) and you will have it trigger every 5:th second
The library is very new and work is ongoing on GitHub https://github.com/fa1k3n/ants.git
I'm doing some multi-threading. I have a worker class with a work method, which I send into a separate QThread. The work method has a conditioned while loop inside. I want to be able to send a signal to the worker object to stop it (changing the _running condition to false). This will cause the while loop to exit, and a finished signal to be sent from the worker object (which is connected to the quit slot of the worker's thread).
The false condition is sent to the worker object via a signal, but it is never received, which I believe is because the while loop blocks the event-loop of its thread. Even if I put QCoreApplication.processEvents() inside the while loop, nothing happens. Where is the problem? Why isn't the signal processed? (Notice that the print statement in the stop slot on the Worker is never executed - but the weird thing is, the thread does seem to stop in a wrong way).
Here is the code:
import time, sys
from PyQt4.QtCore import *
from PyQt4.QtGui import *
class Worker(QObject):
sgnFinished = pyqtSignal()
def __init__(self, parent):
QObject.__init__(self, parent)
self._running = True
#pyqtSlot()
def stop():
print 'stop signal received, switching while loop condition to false'
self._running = False
#pyqtSlot()
def work(self):
while self._running: #this blocks the thread, if changed to an if clause, thread finishes as expected!
QCoreApplication.processEvents() #this doesn't help!
time.sleep(0.1)
print 'doing work...'
#do some cleanup here, then signal the worker is done
self.sgnFinished.emit()
class Client(QObject):
sgnStop = pyqtSignal()
def __init__(self, parent):
QObject.__init__(self, parent)
self._thread = None
self._worker = None
def toggle(self, enable):
if enable:
if not self._thread:
self._thread = QThread()
self._worker = Worker(None)
self._worker.moveToThread(self._thread)
self._worker.sgnFinished.connect(self.on_worker_done)
self.sgnStop.connect(self._worker.stop)
self._thread.started.connect(self._worker.work)
self._thread.start()
else:
print 'sending stop signal to the worker object'
self.sgnStop.emit() #send a queuedconnection type signal to the worker, because its in another thread
#pyqtSlot()
def on_worker_done(self):
print 'workers job was interrupted manually'
self._thread.quit()
#self._thread.wait() not sure this is neccessary
if __name__ == '__main__':
app = QCoreApplication(sys.argv)
client = Client(None)
client.toggle(True)
raw_input('Press something')
client.toggle(False)
There are two main problems in your example:
Firstly, you are emitting a signal to stop the worker, but since the signal is cross-thread, it will be posted in the receiver's event-queue. However, the worker is running a blocking while-loop, so pending events cannot be processed. There are a few ways to work around this, but probably the simplest is to simply call the worker's stop method directly instead of using a signal.
Secondly, you are not explicitly running an event-loop in the main thread, so cross-thread signals sent from the worker cannot be queued. More importantly, though, there is also nothing to stop the program exiting after the user presses a key - so the client and worker will be immediately garbage-collected.
Below is a re-written version of your example which fixes all the issues:
import time, sys
from PyQt4.QtCore import *
from PyQt4.QtGui import *
class Worker(QObject):
sgnFinished = pyqtSignal()
def __init__(self, parent):
QObject.__init__(self, parent)
self._mutex = QMutex()
self._running = True
#pyqtSlot()
def stop(self):
print 'switching while loop condition to false'
self._mutex.lock()
self._running = False
self._mutex.unlock()
def running(self):
try:
self._mutex.lock()
return self._running
finally:
self._mutex.unlock()
#pyqtSlot()
def work(self):
while self.running():
time.sleep(0.1)
print 'doing work...'
self.sgnFinished.emit()
class Client(QObject):
def __init__(self, parent):
QObject.__init__(self, parent)
self._thread = None
self._worker = None
def toggle(self, enable):
if enable:
if not self._thread:
self._thread = QThread()
self._worker = Worker(None)
self._worker.moveToThread(self._thread)
self._worker.sgnFinished.connect(self.on_worker_done)
self._thread.started.connect(self._worker.work)
self._thread.start()
else:
print 'stopping the worker object'
self._worker.stop()
#pyqtSlot()
def on_worker_done(self):
print 'workers job was interrupted manually'
self._thread.quit()
self._thread.wait()
if raw_input('\nquit application [Yn]? ') != 'n':
qApp.quit()
if __name__ == '__main__':
# prevent some harmless Qt warnings
pyqtRemoveInputHook()
app = QCoreApplication(sys.argv)
client = Client(None)
def start():
client.toggle(True)
raw_input('Press something\n')
client.toggle(False)
QTimer.singleShot(10, start)
sys.exit(app.exec_())
Cross thread signal/slot connections require a running event loop in the thread of the receiver object.
In your case there is an event loop in the second thread and it is running, but it is at all times executing your work method and never returns from there.
So all slot invocation events are stuck in the event loop's event queue.
If you want to hack around this, like you attempted with QCoreApplication.processEvents you could try getting the thread's eventDispatcher and calling its processEvent.
If you only need to end the worker, you could call the thread's requestInteruption and instead of checking for self._running you check for the thread's isInterruptionRequested.
I have created a program to generate data points of functions that I later plot. The program takes a class which defines the function, creates a data outputting object which when called generates the data to a text file. To make the whole process faster I put the jobs in threads, however when I do, the data generated is not always correct. I have attached a picture to show what I mean:
Here are some of the relevant bits of code:
from queue import Queue
import threading
import time
queueLock = threading.Lock()
workQueue = Queue(10)
def process_data(threadName, q, queue_window, done):
while not done.get():
queueLock.acquire() # check whether or not the queue is locked
if not workQueue.empty():
data = q.get()
# data is the Plot object to be run
queueLock.release()
data.parent_window = queue_window
data.process()
else:
queueLock.release()
time.sleep(1)
class WorkThread(threading.Thread):
def __init__(self, threadID, q, done):
threading.Thread.__init__(self)
self.ID = threadID
self.q = q
self.done = done
def get_qw(self, queue_window):
# gets the queue_window object
self.queue_window = queue_window
def run(self):
# this is called when thread.start() is called
print("Thread {0} started.".format(self.ID))
process_data(self.ID, self.q, self.queue_window, self.done)
print("Thread {0} finished.".format(self.ID))
class Application(Frame):
def __init__(self, etc):
self.threads = []
# does some things
def makeThreads(self):
for i in range(1, int(self.threadNum.get()) +1):
thread = WorkThread(i, workQueue, self.calcsDone)
self.threads.append(thread)
# more code which just processes the function etc, sorts out the gui stuff.
And in a separate class (as I'm using tkinter, so the actual code to get the threads to run is called in a different window) (self.parent is the Application class):
def run_jobs(self):
if self.running == False:
# threads are only initiated when jobs are to be run
self.running = True
self.parent.calcsDone.set(False)
self.parent.threads = [] # just to make sure that it is initially empty, we want new threads each time
self.parent.makeThreads()
self.threads = self.parent.threads
for thread in self.threads:
thread.get_qw(self)
thread.start()
# put the jobs in the workQueue
queueLock.acquire()
for job in self.job_queue:
workQueue.put(job)
queueLock.release()
else:
messagebox.showerror("Error", "Jobs already running")
This is all the code which relates to the threads.
I don't know why when I run the program with multiple threads some data points are incorrect, whilst running it with just 1 single thread the data is all perfect. I tried looking up "threadsafe" processes, but couldn't find anything.
Thanks in advance!
I am experimenting with threading for a project I am working on. Here is the code I am using as a test
import threading
class one(threading.Thread):
def __init__(self):
threading.Thread.__init__(self)
while 1:
print "one"
class two(threading.Thread):
def __init__(self):
threading.Thread.__init__(self)
while 1:
print "two"
threads = []
one = one()
two = two()
one.start()
two.start()
threads.append(one)
threads.append(two)
for t in threads:
t.join()
The problem is that only class one runs. Can you see a problem with my code?
You have to override the run method, not __init__:
class one(threading.Thread):
def run(self):
while 1:
print "one"
This method is what is executed on a different thread, while one = one() starts an infinite loop in the same thread that the object is created.
Override __init__ if you want to pass an argument to be used in the new thread, for instance:
class NumberedThread(threading.Thread):
def __init__(self, number):
threading.Thread.__init__(self)
self.number = number
def run(self):
while 1:
print self.number
NumberedThread("one").start()
NumberedThread("two").start()
You've put an infinite loop in your thread constructor. Your first "thread" never even gets out of its constructor, so the code that's trying to create it just sits and waits for the object to be created. As a result, you aren't actually multithreading anything: you've just got an infinite loop in the main thread.
Override run instead of __init__ and you should be all set.
class one(threading.Thread):
def run(self):
while 1:
print "one"
class two(threading.Thread):
def run(self):
while 1:
print "two"