Cannot start new python thread

Question

I have following python code. I would like to start new thread after the button is pressed because I would like to do something else with main thread. But code currently, I have does not seem to create a new thread when checked from pycharm concurrency diagram. I can only start new thread when I press the button. Also the program does not respond after pressing the button. Please help.

from PyQt4 import QtCore, QtGui
import sys
import subprocess
import re
import threading
sys.settrace
try:
 _fromUtf8 = QtCore.QString.fromUtf8
except AttributeError:
 def _fromUtf8(s):
 return s
try:
 _encoding = QtGui.QApplication.UnicodeUTF8
 def _translate(context, text, disambig):
 return QtGui.QApplication.translate(context, text, disambig, _encoding)
except AttributeError:
 def _translate(context, text, disambig):
 return QtGui.QApplication.translate(context, text, disambig)
class GuiMainWindow(QtGui.QMainWindow):
 def setupUi(self, MainWindow):
 MainWindow.setObjectName(_fromUtf8("MainWindow"))
 MainWindow.resize(420, 280)
 self.centralwidget = QtGui.QWidget(MainWindow)
 self.buttonTrans = QtGui.QPushButton(self.centralwidget)
 self.buttonTrans.setGeometry(QtCore.QRect(50, 110, 131, 51))
 self.buttonTrans.setObjectName(_fromUtf8("buttonTrans"))
 self.label = QtGui.QLabel(self.centralwidget)
 self.label.setGeometry(QtCore.QRect(70, 60, 281, 21))
 MainWindow.setCentralWidget(self.centralwidget)
 self.retranslateUi(MainWindow)
 QtCore.QMetaObject.connectSlotsByName(MainWindow)
 print(self)
 def retranslateUi(self, MainWindow):
 self.buttonTrans.setText(_translate("MainWindow", "Start", None))
 self.connect(self.buttonTrans, QtCore.SIGNAL('clicked()'), self.setup_video)
 def setup_video(self):
 print("Setting up VIDEO")
 t = threading.Thread(target=self.logging_thread()).start()
 def logging_thread(self):
 cmd33 = "ping www.google.com"
 cmd3process = subprocess.Popen(cmd33.split(), stdout=subprocess.PIPE, shell=True)
 import time
 while True:
 output3 = cmd3process.stdout.readline()
 time.sleep(1)
 if output3 == '' and cmd3process.poll() != None:
 break
 print(output3.decode("utf-8"))
if __name__ == "__main__":
 import sys
 app = QtGui.QApplication(sys.argv)
 MainWindow = QtGui.QMainWindow()
 ui = GuiMainWindow()
 ui.setupUi(MainWindow)
 MainWindow.show()
 sys.exit(app.exec_())

• Mad Physicist: How do you know it does not create a new thread?
• Main: Because when I ran the code in pycharm concurrency, I can only see only main thread. I cannot see new thread after button is pressed
• Mad Physicist: Fair enough. Put that in your question and I will retract my close vote.
• Main: Yes. The python program becomes not responding
• Tamas Hegedus: What does it print? Does it print "Setting up VIDEO"?

Answer 1

You invoke the method instead of passing it as a parameter to the new Thread here:

t = threading.Thread(target=self.logging_thread()).start()

Change it to:

t = threading.Thread(target=self.logging_thread).start()

• Mad Physicist: @Main This is definitely a problem. Combine that with my recommendation and see if anything happens.
• Main: Yes. This has been a problem.

Answer 2

Most likely, an exception is occurring in your thread. To identify and fix it try the following:

def logging_thread(self):
 try:
 cmd33 = "ping www.google.com"
 cmd3process = subprocess.Popen(cmd33.split(), stdout=subprocess.PIPE, shell=True)
 import time
 while True:
 output3 = cmd3process.stdout.readline()
 time.sleep(1)
 if output3 == '' and cmd3process.poll() != None:
 break
 print(output3.decode("utf-8"))
 except:
 import traceback
 traceback.print_exc

When you have identified the cause of the error, you have two options:

1. If the error is something you did (e.g. a mistyped attribute), remove the try...except block entirely.
2. If there is a condition in your code that may legitimately occur, retain the block but make the exception type-specific. For example except ValueError:. Also, improve the actual handler in that case.

• Main: I added try-except blocks as you suggested. But still there is no console exceptions I could see. The program still goes unresponsive. Please help