PyQt5 Qthread Create - qt

AttributeError: type object 'QThread' has no attribute 'create'
Here is my code.
from PyQt5.QtCore import QThread
def fun(num):
print(num)
thread1 = QThread.create(fun)
thread1.start()
But Qt documentation says there is a function called create since Qt 5.10. I am using PyQt5 5.11.3. Someone please help me with this.

You can use worker objects by moving them to the thread using QObject::moveToThread().
from PyQt5.QtCore import QObject, pyqtSignal, QThread, QTimer
from PyQt5.QtWidgets import QApplication, QWidget, QVBoxLayout, QProgressBar, QPushButton
class Worker(QObject):
valueChanged = pyqtSignal(int) # Value change signal
def run(self):
print('thread id ->', int(QThread.currentThreadId()))
for i in range(1, 101):
print('value =', i)
self.valueChanged.emit(i)
QThread.msleep(100)
class Window(QWidget):
def __init__(self, *args, **kwargs):
super(Window, self).__init__(*args, **kwargs)
layout = QVBoxLayout(self)
self.progressBar = QProgressBar(self)
self.progressBar.setRange(0, 100)
layout.addWidget(self.progressBar)
layout.addWidget(QPushButton('Open thread', self, clicked=self.onStart))
# Current thread id
print('main id = ', int(QThread.currentThreadId()))
# Start thread update progress bar value
self._thread = QThread(self)
self._worker = Worker()
self._worker.moveToThread(self._thread) # Move to thread to execute
self._thread.finished.connect(self._worker.deleteLater)
self._worker.valueChanged.connect(self.progressBar.setValue)
def onStart(self):
print('main id -> ', int(QThread.currentThreadId()))
self._thread.start() # Start thread
QTimer.singleShot(1, self._worker.run)
def closeEvent(self, event):
if self._thread.isRunning():
self._thread.quit()
del self._thread
del self._worker
super(Window, self).closeEvent(event)
if __name__ == '__main__':
import sys
app = QApplication(sys.argv)
w = Window()
w.show()
w.setWindowTitle('Demo moveToThread')
sys.exit(app.exec_())

Related

How do I pass a variable to a QThread object when creating an instance? I'm getting a type error in Qthread.__init__

I found this sample code using QThread at https://doc.qt.io/qtforpython/examples/example_widgets__thread_signals.html
I modified the code in an attempt to pass a variable to the thread when instantiated based on info I found here: https://nikolak.com/pyqt-threading-tutorial/
Unfortunately I am getting the following error:
Traceback (most recent call last):
File "C:\Users\joe\python\ThreadTest.py", line 22, in start_thread
instanced_thread = WorkerThread(self, 'c:\testfile.xml')
File "C:\Users\joe\python\ThreadTest.py", line 44, in __init__
QThread.__init__(self, parent)
TypeError: 'PySide6.QtCore.QThread.__init__' called with wrong argument types:
PySide6.QtCore.QThread.__init__(str)
Supported signatures:
PySide6.QtCore.QThread.__init__(Optional[PySide6.QtCore.QObject] = None)
Can someone tell me the proper syntax for passing a variable to a QThread?
I'm using PySide6 and Python 3.9.10.
# Copyright (C) 2022 The Qt Company Ltd.
# SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
import sys
from PySide6.QtCore import QObject, QThread, Signal, Slot
from PySide6.QtWidgets import QApplication, QPushButton, QVBoxLayout, QWidget
# Create a basic window with a layout and a button
class MainForm(QWidget):
def __init__(self):
super().__init__()
self.setWindowTitle("My Form")
self.layout = QVBoxLayout()
self.button = QPushButton("Click me!")
self.button.clicked.connect(self.start_thread)
self.layout.addWidget(self.button)
self.setLayout(self.layout)
# Instantiate and start a new thread
def start_thread(self):
instanced_thread = WorkerThread(self, 'c:\testfile.xml')
instanced_thread.start()
# Create the Slots that will receive signals
#Slot(str)
def update_str_field(self, message):
print(message)
#Slot(int)
def update_int_field(self, value):
print(value)
# Signals must inherit QObject
class MySignals(QObject):
signal_str = Signal(str)
signal_int = Signal(int)
# Create the Worker Thread
class WorkerThread(QThread):
def __init__(self, filename, parent=None):
QThread.__init__(self, parent)
# Instantiate signals and connect signals to the slots
self.signals = MySignals()
self.signals.signal_str.connect(parent.update_str_field)
self.signals.signal_int.connect(parent.update_int_field)
self.filename = filename
def run(self):
# Do something on the worker thread
a = 1 + 1
# Emit signals whenever you want
self.signals.signal_int.emit(a)
self.signals.signal_str.emit("This text comes to Main thread from our Worker thread.")
print(self.filename)
if __name__ == "__main__":
app = QApplication(sys.argv)
window = MainForm()
window.show()
sys.exit(app.exec())

QWidget painter

I have this code:
import sys, random, pprint
from PyQt5 import QtWidgets, QtGui, QtCore
from PyQt5 import QtGui
from PyQt5.QtCore import Qt
class Window(QtWidgets.QMainWindow):
def __init__(self):
super().__init__()
self.initUI()
def initUI(self):
self.setGeometry(QtCore.QRect(200, 200, 700, 700))
self.widget = QtWidgets.QWidget(self)
self.widget.setGeometry(QtCore.QRect(10, 10, 400, 200))
self.widget.setObjectName("widget")
def paintEvent(self, event):
painter = QtGui.QPainter()
painter.begin(self.widget)
self.drawPoints(painter)
painter.end()
def drawPoints(self, painter):
#drawing code
if __name__ == '__main__':
app = QtWidgets.QApplication(sys.argv)
ex = Window()
ex.show()
sys.exit(app.exec_())
What do i expect: area (400x200) which would be painted by drawPoints(). QWidget inherits QPaintDevice. So this code should work. But console says:
QPainter::begin: Paint device returned engine == 0, type: 1
QPainter::end: Painter not active, aborted
Could you help me, please.
It looks like you are attempting to replicate this example, correct?
The major difference appears to be that you are defining paintEvent() for the main window, rather than the widget you are actually trying to paint. It would work if you created a custom subclass of QWidget, defined paintEvent() there, and then inserted that into a standard QMainWindow instance, like this:
class MyWidget(QtWidgets.QWidget):
def __init__(self, parent=None):
super(MyWidget, self).__init__(parent=parent)
self.initUI()
def initUI(self):
self.setGeometry(QtCore.QRect(10, 10, 400, 200))
self.setObjectName("widget")
def paintEvent(self, event):
painter = QtGui.QPainter()
painter.begin(self)
self.drawPoints(painter)
painter.end()
def drawPoints(self, painter):
pass
if __name__ == '__main__':
app = QtWidgets.QApplication(sys.argv)
my_window = QtWidgets.QMainWindow()
my_window.setGeometry(QtCore.QRect(200, 200, 700, 700))
my_window.setCentralWidget(MyWidget(my_window))
my_window.show()
sys.exit(app.exec_())
At the very least, it isn't printing that error message anymore.

Native Qt signal is not callable in PyCharm

I created a QMainWindow with menu and tools :
import sys
from PyQt4 import QtGui
class Example(QtGui.QMainWindow):
def __init__(self):
super(Example, self).__init__()
self.initUI()
Then, I created a quit action by shortcut :
def initUI(self):
exitaction=QtGui.QAction(QtGui.QIcon('exit.png'),'&Exit',self)
exitaction.setShortcut('Ctrl+Q')
exitaction.setStatusTip('EXIT application')
Now : pycharm tells me it can't find reference qApp in __init__.py :
exitaction.triggered().connect(QtGui.qApp.quit)
self.statusBar()
menubar=self.menuBar()
fileMenu=menubar.addMenu('&File')
fileMenu.addAction(exitaction)
self.setGeometry(300,300,250,150)
self.setWindowTitle('Menubar')
self.show()
def main():
app=QtGui.QApplication(sys.argv)
ex=Example()
sys.exit(app.exec_())
def main():
app = QtGui.QApplication(sys.argv)
ex = Example()
sys.exit(app.exec_())
if __name__ == '__main__':
main()
Try to use QApplication istead of QtGui.qapp:
exitaction.triggered().connect(QApplication.instance().quit)
Compare the answer to: calling quit() method of QApplication

PyQt: connecting slots with custom objects via Qt Designer

I have a PyQt widget that sends signals with numpy.ndarray data. And I have another PyQt widget that has a slot with numpy.ndarray data.
Both widget are located on my main window, that is compiled from *.ui file. The widgets are set as promoted widgets.
Cannot I somehow connect the signal and slot in Qt Creator?
Just now it gives me the next error:
TypeError: C++ type 'ndarray' is not supported as a slot argument type
Reason for this is Qt only support the datatype defined in QMetaType passed as argument of signal, looks here http://pyqt.sourceforge.net/Docs/PyQt4/qmetatype.html#Q_DECLARE_METATYPE
According to ekhumoro's POST, I update the following code, it should work for PyQt4, not tested on PyQt5.
from PyQt4.QtGui import *
from PyQt4.QtCore import *
from numpy import *
class MyThread(QThread):
mysignal = pyqtSignal(ndarray)
def __init__(self, parent=None):
super(MyThread, self).__init__(parent)
def run(self):
while True:
QThread.msleep(100)
self.mysignal.emit(array((1, 2, 3, 4)))
class MyWidget(QWidget):
def __init__(self, parent=None):
super(MyWidget, self).__init__(parent)
self.thread = MyThread()
self.thread.mysignal.connect(self.handleSignal)
self.thread.start()
def handleSignal(self, data):
print data
if __name__ == '__main__':
import sys
app = QApplication(sys.argv)
w = MyWidget()
w.show()
app.exec_()

Passing exception to slot while emitting signal

I have to pass what exception occured in one function to a slot inside a different class.
_qObject = QtCore.QObject()
except Exception, ex:
QtCore.QObject.emit(_qObject, QtCore.SIGNAL("error_occured"))
I want to pass ex to class that has
QtCore.QObject.connect(_qObject, QtCore.SIGNAL("error_occured"), self.__errorOccured)
This is my case
from PyQt4.QtCore import pyqtSignal, pyqtSlot
from PyQt4.QtGui import QWidget, QApplication
has_error = pyqtSignal(Exception)
class SomeOtherClass(QWidget):
# this is my UI class
def __init__(self, parent=None):
super(SomeOtherClass, self).__init__(parent)
# Initialise the Class and connect signal to slot
has_error.connect(self.thrown_error)
#pyqtSlot(Exception)
def thrown_error(self, my_err):
#Do Stuff with the Exception
print(type(my_err), my_err)
self.close()
def makeError():
try:
print 1/0
except ZeroDivisionError, ze:
has_error.emit(ze)
app = QApplication([])
SomeOtherClass()
See below code for example:
from PyQt4.QtCore import pyqtSignal, pyqtSlot
from PyQt4.QtGui import QWidget, QApplication
import sys
class SomeClass(QWidget):
# Declare a new signal - passes Exception
has_error = pyqtSignal(Exception)
def __init__(self, parent=None):
super(SomeClass, self).__init__(parent)
def run_something(self):
#Force an Error
try:
1 / 0
except ZeroDivisionError as ze:
#Emit the Signal
self.has_error.emit(ze)
class SomeOtherClass(QWidget):
def __init__(self, parent=None):
super(SomeOtherClass, self).__init__(parent)
# Initialise the Class and connect signal to slot
class1 = SomeClass()
class1.has_error.connect(self.thrown_error)
class1.run_something()
#pyqtSlot(Exception)
def thrown_error(self, my_err):
#Do Stuff with the Exception
print(type(my_err), my_err)
app = QApplication(sys.argv)
SomeOtherClass()
See the new way to connect signals to slots
How Shadow9043 suggested is also right but in comments things got twisted but this is what I found the correct and simplistic approach.
Long Story in Short!!!
except Exception, ex:
QtCore.QObject.emit(_qObject, QtCore.SIGNAL("error_occured"), str(ex))
and in the class where I connect this exception
i will take this ex string as argument
def __errorOccured(self, exStr):
print exStr
Here is how I have it working, if anyone has got better suggestion in how I achieved it please comment.
from PyQt4.QtCore import pyqtSignal, pyqtSlot
from PyQt4.QtGui import QWidget, QApplication
from PyQt4 import QtCore
import sys
_qObject = QtCore.QObject()
class SomeOtherClass(QWidget):
# this is my UI class
def __init__(self, parent=None):
super(SomeOtherClass, self).__init__(parent)
# Initialise the Class and connect signal to slot
QtCore.QObject.connect(_qObject, QtCore.SIGNAL("error_occured"), self.thrown_error)
def thrown_error(self, my_err):
#Do Stuff with the Exception
print(type(my_err), my_err)
def makeError():
try:
print 1/0
except ZeroDivisionError, ex:
QtCore.QObject.emit(_qObject, QtCore.SIGNAL("error_occured"), str(ex))
app = QApplication(sys.argv)
win = SomeOtherClass()
makeError()
win.show()
sys.exit(app.exec_())

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