Based on the Worker objects methods mentioned in other answers, I decided to see if I could expand on the solution to invoke more threads - in this case the optimal number the machine can run and spin up multiple workers with indeterminate completion times.
To do this I still need to subclass QThread - but only to assign a thread number and to 'reimplement' the signals 'finished' and 'started' to include their thread number.
I've focused quite a bit on the signals between the main gui, the threads, and the workers.
Similarly, others answers have been a pains to point out not parenting the QThread but I don't think this is a real concern. However, my code also is careful to destroy the QThread objects.
However, I wasn't able to parent the worker objects so it seems desirable to send them the deleteLater() signal, either when the thread function is finished or the GUI is destroyed. I've had my own code hang for not doing this.
Another enhancement I felt was necessary was was reimplement the closeEvent of the GUI (QWidget) such that the threads would be instructed to quit and then the GUI would wait until all the threads were finished. When I played with some of the other answers to this question, I got QThread destroyed errors.
Perhaps it will be useful to others. I certainly found it a useful exercise. Perhaps others will know a better way for a thread to announce it identity.
#!/usr/bin/env python3
#coding:utf-8
# Author: --<>
# Purpose: To demonstrate creation of multiple threads and identify the receipt of thread results
# Created: 19/12/15
import sys
from PyQt4.QtCore import QThread, pyqtSlot, pyqtSignal
from PyQt4.QtGui import QApplication, QLabel, QWidget, QGridLayout
import sys
import worker
class Thread(QThread):
#make new signals to be able to return an id for the thread
startedx = pyqtSignal(int)
finishedx = pyqtSignal(int)
def __init__(self,i,parent=None):
super().__init__(parent)
self.idd = i
self.started.connect(self.starttt)
self.finished.connect(self.finisheddd)
@pyqtSlot()
def starttt(self):
print('started signal from thread emitted')
self.startedx.emit(self.idd)
@pyqtSlot()
def finisheddd(self):
print('finished signal from thread emitted')
self.finishedx.emit(self.idd)
class Form(QWidget):
def __init__(self):
super().__init__()
self.initUI()
self.worker={}
self.threadx={}
self.i=0
i=0
#Establish the maximum number of threads the machine can optimally handle
#Generally relates to the number of processors
self.threadtest = QThread(self)
self.idealthreadcount = self.threadtest.idealThreadCount()
print("This machine can handle {} threads optimally".format(self.idealthreadcount))
while i <self.idealthreadcount:
self.setupThread(i)
i+=1
i=0
while i<self.idealthreadcount:
self.startThread(i)
i+=1
print("Main Gui running in thread {}.".format(self.thread()))
def setupThread(self,i):
self.worker[i]= worker.Worker(i) # no parent!
#print("Worker object runningt in thread {} prior to movetothread".format(self.worker[i].thread()) )
self.threadx[i] = Thread(i,parent=self) # if parent isn't specified then need to be careful to destroy thread
self.threadx[i].setObjectName("python thread{}"+str(i))
#print("Thread object runningt in thread {} prior to movetothread".format(self.threadx[i].thread()) )
self.threadx[i].startedx.connect(self.threadStarted)
self.threadx[i].finishedx.connect(self.threadFinished)
self.worker[i].finished.connect(self.workerFinished)
self.worker[i].intReady.connect(self.workerResultReady)
#The next line is optional, you may want to start the threads again without having to create all the code again.
self.worker[i].finished.connect(self.threadx[i].quit)
self.threadx[i].started.connect(self.worker[i].procCounter)
self.destroyed.connect(self.threadx[i].deleteLater)
self.destroyed.connect(self.worker[i].deleteLater)
#This is the key code that actually get the worker code onto another processor or thread.
self.worker[i].moveToThread(self.threadx[i])
def startThread(self,i):
self.threadx[i].start()
@pyqtSlot(int)
def threadStarted(self,i):
print('Thread {} started'.format(i))
print("Thread priority is {}".format(self.threadx[i].priority()))
@pyqtSlot(int)
def threadFinished(self,i):
print('Thread {} finished'.format(i))
@pyqtSlot(int)
def threadTerminated(self,i):
print("Thread {} terminated".format(i))
@pyqtSlot(int,int)
def workerResultReady(self,j,i):
print('Worker {} result returned'.format(i))
if i ==0:
self.label1.setText("{}".format(j))
if i ==1:
self.label2.setText("{}".format(j))
if i ==2:
self.label3.setText("{}".format(j))
if i ==3:
self.label4.setText("{}".format(j))
#print('Thread {} has started'.format(self.threadx[i].currentThreadId()))
@pyqtSlot(int)
def workerFinished(self,i):
print('Worker {} finished'.format(i))
def initUI(self):
self.label1 = QLabel("0")
self.label2= QLabel("0")
self.label3= QLabel("0")
self.label4 = QLabel("0")
grid = QGridLayout(self)
self.setLayout(grid)
grid.addWidget(self.label1,0,0)
grid.addWidget(self.label2,0,1)
grid.addWidget(self.label3,0,2)
grid.addWidget(self.label4,0,3) #Layout parents the self.labels
self.move(300, 150)
self.setGeometry(0,0,300,300)
#self.size(300,300)
self.setWindowTitle('thread test')
self.show()
def closeEvent(self, event):
print('Closing')
#this tells the threads to stop running
i=0
while i <self.idealthreadcount:
self.threadx[i].quit()
i+=1
#this ensures window cannot be closed until the threads have finished.
i=0
while i <self.idealthreadcount:
self.threadx[i].wait()
i+=1
event.accept()
if __name__=='__main__':
app = QApplication(sys.argv)
form = Form()
sys.exit(app.exec_())
And the worker code below
#!/usr/bin/env python3
#coding:utf-8
# Author: --<>
# Purpose: Stack Overflow
# Created: 19/12/15
import sys
import unittest
from PyQt4.QtCore import QThread, QObject, pyqtSignal, pyqtSlot
import time
import random
class Worker(QObject):
finished = pyqtSignal(int)
intReady = pyqtSignal(int,int)
def __init__(self, i=0):
'''__init__ is called while the worker is still in the Gui thread. Do not put slow or CPU intensive code in the __init__ method'''
super().__init__()
self.idd = i
@pyqtSlot()
def procCounter(self): # This slot takes no params
for j in range(1, 10):
random_time = random.weibullvariate(1,2)
time.sleep(random_time)
self.intReady.emit(j,self.idd)
print('Worker {0} in thread {1}'.format(self.idd, self.thread().idd))
self.finished.emit(self.idd)
if __name__=='__main__':
unittest.main()
self.finishedsignal? For instance, if instead of just printing the count, I want to display the value of count in a QSpinBox that is part of my gui from the other class. – Laspisa