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PyQt5 Getting second screen functions to work

how are you doing?
I have been coding for a couple months. I started with Python, now I am trying to learn PyQt5.
I have created two windows using the Designer Tool. I created a subclass for each specific page, so that it wont mess up my software once i make changes in the Designer.
I managed to make my second window open from the first window. It works well. However, nothing works in window 2 when its opened by window 1. However, when i run window 2 by itself, it does not work.
I am sure it is a inheritance problem that I am messing up. It seems my sofware is inheriting the window 2 layout but not its functions.
I have attached the code. Is it possible for someone to help me out? If possible, i would like a brief explanation on how to fix it too. I want to learn so I can teach others as well.
This is my main window:
from nonregusrscreen1 import NonReg
from Main import Ui_MainWindow # needs to import from the main file
from PyQt5 import QtCore, QtGui, QtWidgets #importing PyQt functionality
class mainWin(QtWidgets.QMainWindow, Ui_MainWindow): #mainWin is new subclass. QtWidgets.Whatever the window was / you need to get inheritance from Ui_MainWindow, otherwise you wil lahve to use self.ui.pushbutton....
def __init__(self, *args, **kwargs): #passing arguments from whatever was called
super().__init__(*args, **kwargs)
self.ui = Ui_MainWindow()
self.setupUi(self)
self.pushButton_2.clicked.connect(self.openwindow) # you have to include UI, otherwise it will not work.
def openwindow(self):
self.window = QtWidgets.QDialog()
self.ui = NonReg()
self.ui.setupUi(self.window)
self.window.show()
if __name__ == '__main__':
app = QtWidgets.QApplication([])
w = mainWin()
w.show()
app.exec_()
This is my second window, here you can see the pushbutton_2 function that only works when the file is opened by itself (not opened using the first window)
from nonregusrscreen import Ui_NonRegUserScreen
from PyQt5 import QtCore, QtGui, QtWidgets
class NonReg(QtWidgets.QDialog, Ui_NonRegUserScreen):
def __init__(self, *args, **kwargs):
super().__init__(*args, **kwargs)
self.ui = Ui_NonRegUserScreen
self.setupUi(self)
self.pushButton_2.clicked.connect(self.closewindow)
def closewindow(self):
self.window = exit()
if __name__ == '__main__':
app = QtWidgets.QApplication([])
w = NonReg()
w.show()
app.exec_()
Thank you, i truly appreciate your help.

Qt GUI inside loop?

What I want to achieve is a Qt Widget loop.
Simple example:
UI_dialog is a QDialog and after accepted it will open UI_mainwindow which is a QMainWindow.
There is a button in UI_mainwindow and if clicked, it will close UI_mainwindow and go back to UI_dialog.
What I've done so far:
I've tried:
create while loop in a Qthread which contains the two UI objects call UI_dialog inside UI_mainwindow (kind of succeed but may crash sometimes for my poor design)

In a GUI you must avoid the while True, the GUI already has an internal while True that allows you to listen to the events and according to it do the internal tasks. On the other hand the threads should be your last option since the GUI should not update from another thread directly, it should only be used if there is a blocking task.
In the case of Qt there are signals that allow notification of changes, this will be connected to functions so that the latter is invoked when the signal is emited.
from PyQt5 import QtWidgets
class MainWindow(QtWidgets.QMainWindow):
def __init__(self, parent=None):
super(MainWindow, self).__init__(parent)
self.button = QtWidgets.QPushButton("Press me")
self.setCentralWidget(self.button)
self.button.clicked.connect(self.close)
class Dialog(QtWidgets.QDialog):
def __init__(self, parent=None):
super(Dialog, self).__init__(parent)
buttonBox = QtWidgets.QDialogButtonBox()
buttonBox.setStandardButtons(QtWidgets.QDialogButtonBox.Cancel|QtWidgets.QDialogButtonBox.Ok)
buttonBox.accepted.connect(self.accept)
buttonBox.rejected.connect(self.reject)
lay = QtWidgets.QVBoxLayout(self)
lay.addWidget(buttonBox)
if __name__ == '__main__':
import sys
app = QtWidgets.QApplication(sys.argv)
w1 = MainWindow()
w2 = Dialog()
w1.button.clicked.connect(w2.show)
w2.accepted.connect(w1.show)
w2.show()
sys.exit(app.exec_())

Change Button Color in Qt Thread Python

I need to change the color of QPushButton, but an error occurred: "AttributeError: type object 'ProyectoTFM' has no attribute 'ui'".
I don't know hoy to acced to a ui variable from my thread.
This is my code:
import sys
import OpenOPC
import time
import threading
from proyectoQt import *
def actualizarDatosOPC():
while 1:
time.sleep(5)
if(itemsOPC[15])[1]!=0:
#Error on next line
ProyectoTFM.ui.AP08Button.setStyleSheet("background-color: red")
return
class ProyectoTFM(QtGui.QMainWindow):
def __init__(self,parent=None):
QtGui.QMainWindow.__init__(self,parent)
self.ui = Ui_MainWindow()
self.ui.setupUi(self)
self.startTheThread()
print('Init')
def startTheThread(self):
threadQt = threading.Thread(target = actualizarDatosOPC)
threadQt.start()
def clienteOPC():
opc=OpenOPC.client()
opc.connect('Kepware.KEPServerEX.V6')
global itemsOPC
while 1:
itemsOPC = opc.read(opc.list('PLC.PLC.TAGS'))
time.sleep(5)
return
threads = list()
threadOPC = threading.Thread(target=clienteOPC)
threads.append(threadOPC)
threadOPC.start()
time.sleep(5)
if __name__== "__main__":
app=QtGui.QApplication(sys.argv)
myapp = ProyectoTFM()
myapp.show()
sys.exit(app.exec_())
threadOPC.__delete()
Sorry for my English and thanks.

It is not correct to modify the view from a different thread to the main one, a way to solve the problem without using QThread is to create a signal that connects to some slot that changes the color of the button. To be able to emit the signal from the new thread we must pass the object to him through the parameter args.
def actualizarDatosOPC(obj):
while 1:
time.sleep(5)
if(itemsOPC[15])[1]!=0:
#Error on next line
obj.sendChangeColor.emit()
return
class ProyectoTFM(QtGui.QMainWindow):
sendChangeColor = QtCore.pyqtSignal()
def __init__(self,parent=None):
QtGui.QMainWindow.__init__(self,parent)
self.ui = Ui_MainWindow()
self.ui.setupUi(self)
self.startTheThread()
print('Init')
self.sendChangeColor.connect(lambda: self.ui.AP08Button.setStyleSheet("background-color: red"))
def startTheThread(self):
threadQt = threading.Thread(target = actualizarDatosOPC, args=(self,))
threadQt.start()

Even if you got this to work, you can't modify the UI from a thread directly.

A few things:
You never actually pass the UI to the function actualizarDatosOPC
so it doesn't know it exists.
Is there any reason you can't use PyQt's built in threading tools? If you are going to use PyQt it might make sense to buy into the whole framework.
def startTheThread(self):
self.threadQt = QThread()
d = actualizarDatosOPC(self)
d.moveToThread(self.threadQt)
self.threadQt.start()
def actualizarDatosOPC(widget):
.... widget.AP08Button.setStyleSheet("background-color: red")
If you do choose to go this route, I'd take a look at this thread which has a good example:
How to use QThread correctly in pyqt with moveToThread()?
Additionally, while the way you initialize your Window works, this is the more standard way to do it:
class ProyectoTFM(QMainWindow, Ui_MainWindow):
def __init__(self, parent):
# General Init Stuff
super(Login, self).__init__(parent)
self.setupUi(self)
After that, whenever you want to refer to something in the UI all you need to do is refer to self._____. For example, if you have a button named buttonA, self.buttonA would be the appropriate reference.
Edit:
As mentioned in another answer, the proper way to actually change the button color would be to emit a trigger that to the main thread which could then respond by changing the button color.

PyQt - Modify GUI from another thread

I'm trying to modify my main layout from another thread. But the function run() is never called
and i'm having the error:
QObject::setParent: Cannot set parent, new parent is in a different
thread
Here's my code:
class FeedRetrievingThread(QtCore.QThread):
def __init__(self, parent=None):
super(FeedRetrievingThread, self).__init__(parent)
self.mainLayout = parent.mainLayout
def run(self):
# Do things with self.mainLayout
class MainWindow(QtGui.QDialog):
def __init__(self, parent=None):
super(MainWindow, self).__init__(parent)
self.mainLayout = QtGui.QGridLayout()
self.setLayout(self.mainLayout)
self.feedRetrievingThread = FeedRetrievingThread(self)
self.timer = QtCore.QTimer()
self.timer.timeout.connect(self.updateFeed)
self.timer.start(1000)
def updateFeed(self):
if not self.feedRetrievingThread.isRunning():
print 'Running thread.'
self.feedRetrievingThread.start()
if __name__ == '__main__':
app = QtGui.QApplication(sys.argv)
mainWindow = MainWindow()
mainWindow.show()
sys.exit(app.exec_())
I really don't get it, why is it so difficult to access the GUI with PyQt?
In C# you have Invoke. Is there anything of the kind in PyQt?
I tried creating the thread directly from MainWindow.__init__ (without using the timer) but it didn't work either.

In Qt you should never attempt to directly update the GUI from outside of the GUI thread.
Instead, have your threads emit signals and connect them to slots which do the necessary updating from within the GUI thread.
See the Qt documentation regarding Threads and QObjects.

How to connect a signal from the controller in PyQt4? (iOS like MVC structure in PyQt4)

Why doesn't the following example work?
from PyQt4 import QtGui
import sys
class TestView(QtGui.QWidget):
def __init__(self):
super(TestView, self).__init__()
self.initUI()
def initUI(self):
self.btn = QtGui.QPushButton('Button', self)
self.btn.resize(self.btn.sizeHint())
self.btn.move(50, 50)
class TestViewController():
def __init__(self, view):
view.btn.clicked.connect(self.buttonClicked)
view.show()
def buttonClicked(self):
print 'clicked'
def main():
app = QtGui.QApplication(sys.argv)
view = TestView()
TestViewController(view)
app.exec_()
if __name__ == '__main__':
main()
The example is supposed to represent an MVC structure (like the one in Figure 4 -- without the Model) where the controller (TestViewController) receives a reference to the view (TestView) and connects the clicked signal from the view's button view.btn to its function self.buttonClicked.
I'm sure the line view.btn.clicked.connect(self.buttonClicked) is executed but, apparently, it has no effect. Does anyone knows how to solve that?
Update (awful solution):
In the example, if I replace the line
view.btn.clicked.connect(self.buttonClicked)
with
view.clicked = self.clicked
view.btn.clicked.connect(view.clicked)
it works. I'm still not happy with that.

The reason it is not working is because the controller class is being garbage collected before you can ever click anything for it.
When you set view.clicked = self.clicked, what you're actually doing is making one of the objects from the controller persist on the view object so it never gets cleaned up - which isn't really the solution.
If you store your controller to a variable, it will protect it from collection.
So if you change your code above to read:
ctrl = TestViewController(view)
You'll be all set.
That being said - what exactly you are trying to do here, I am not sure...it seems you're trying to setup an MVC system for Qt - but Qt already has a pretty good system for that using the Qt Designer to separate the interface components into UI (view/template) files from controller logic (QWidget subclasses). Again, I don't know what you are trying to do and this may be a dumb down version of it, but I'd recommend making it all one class like so:
from PyQt4 import QtGui
import sys
class TestView(QtGui.QWidget):
def __init__(self):
super(TestView, self).__init__()
self.initUI()
def initUI(self):
self.btn = QtGui.QPushButton('Button', self)
self.btn.resize(self.btn.sizeHint())
self.btn.move(50, 50)
self.btn.clicked.connect(self.buttonClicked)
def buttonClicked(self):
print 'clicked'
def main():
app = QtGui.QApplication(sys.argv)
view = TestView()
view.show()
app.exec_()
if __name__ == '__main__':
main()
Edit: Clarifying the MVC of Qt
So this above example doesn't actually load the ui dynamically and create a controller/view separation. Its a bit hard to show on here. Best to work through some Qt/Designer based examples/tutorials - I have one here http://bitesofcode.blogspot.com/2011/10/introduction-to-designer.html but many can be found online.
The short answer is, your loadUi method can be replace with a PyQt4.uic dynamic load (and there are a number of different ways to set that up) such that your code ultimately reads something like this:
from PyQt4 import QtGui
import PyQt4.uic
import sys
class TestController(QtGui.QWidget):
def __init__(self):
super(TestController, self).__init__()
# load view
uifile = '/path/to/some/widget.ui'
PyQt4.uic.loadUi(uifile, self)
# create connections (assuming there is a widget called 'btn' that is loaded)
self.btn.clicked.connect(self.buttonClicked)
def buttonClicked(self):
print 'clicked'
def main():
app = QtGui.QApplication(sys.argv)
view = TestController()
view.show()
app.exec_()
if __name__ == '__main__':
main()
Edit 2: Storing UI references
If it is easier to visualize this concept, you Can also store a reference to the generated UI object:
from PyQt4 import QtGui
import PyQt4.uic
import sys
class TestController(QtGui.QWidget):
def __init__(self):
super(TestController, self).__init__()
# load a view from an external template
uifile = '/path/to/some/widget.ui'
self.ui = PyQt4.uic.loadUi(uifile, self)
# create connections (assuming there is a widget called 'btn' that is loaded)
self.ui.btn.clicked.connect(self.buttonClicked)
def buttonClicked(self):
print 'clicked'
def main():
app = QtGui.QApplication(sys.argv)
view = TestController()
view.show()
app.exec_()
if __name__ == '__main__':
main()