Develop Reference

Why does this PyQt5 Qlistwidget signal + slot not working?

I've been trying to make this work, but it just doesn't. I get no errors, just plain noncompliance. It just does not want to add the QListWidget items, or change the QLabel.
I made a MainWindowClass. It it's main widget I have a layout and a button. In it's dockwidget I have a QListWidget.
I made a signal from the button and connected it to a slot in the dockwidget's list.
The connection is there. When I press the button, the method in the dockwidgetcontents class is running.
But it does not add the items to the listwidget. And does not produce any errors.
Here is the code:
from PyQt5.QtWidgets import *
from PyQt5.QtGui import *
from PyQt5.QtCore import *
import sys
class AppClass:
def __init__(self):
super().__init__()
app = QApplication(sys.argv)
window = MainWindowClass()
window.show()
sys.exit(app.exec_())
class MainWindowClass(QMainWindow):
def __init__(self):
super().__init__()
self.init_UI()
self.TheDockWidget()
def init_UI(self):
self.setGeometry(100, 100, 400, 200)
self.setWindowTitle("Test App")
self.setCentralWidget(MainWidgetClass())
def TheDockWidget(self):
self.dockWidget = QDockWidget('Status:')
self.dockWidget.setFeatures(QDockWidget.DockWidgetMovable | QDockWidget.DockWidgetFloatable)
self.addDockWidget(Qt.RightDockWidgetArea, self.dockWidget)
self.dockWidget.setSizePolicy(QSizePolicy(QSizePolicy.Minimum, QSizePolicy.Minimum))
self.dockWidget.setWidget(DockWidgetContents())
class DockWidgetContents(QWidget):
def __init__(self):
super().__init__()
self.init_UI()
def init_UI(self):
layout = QVBoxLayout()
self.setLayout(layout)
self.button3 = QPushButton()
self.button3.setText("button3")
layout.addWidget(self.button3)
self.listwidget = QListWidget()
layout.addWidget(self.listwidget)
self.listwidget.addItem("Ready.")
self.label = QLabel("initial")
layout.addWidget(self.label)
#pyqtSlot(str, str, int)
def _add_item(self, strA, strB, int1):
self.label.setText("yes") # why does this not work??
self.listwidget.addItem(strA) # why does this not work??
self.listwidget.addItem(strB) # why does this not work??
self.listwidget.addItem(str(int1)) # why does this not work??
print(strA, strB, int1) # but this works fine.
class MainWidgetClass(QWidget):
def __init__(self):
super().__init__()
self.init_UI()
def init_UI(self):
mainLayout = QGridLayout()
self.setLayout(mainLayout)
mainLayout.addWidget(TopLeftWidgetClass(), 0, 0)
class TopLeftWidgetClass(QWidget):
signal = pyqtSignal(str, str, int)
def __init__(self):
super().__init__()
self.init_UI()
def init_UI(self):
layout = QHBoxLayout()
self.setLayout(layout)
self.button1 = QPushButton("button1")
layout.addWidget(self.button1)
self.button1.clicked.connect(self.start)
def start(self):
otherClass = DockWidgetContents()
self.signal.connect(otherClass._add_item)
self.signal.emit("one", "two", 3)
if __name__ == '__main__':
AppClass()
I also read all the suggested questions when I typed my question into the form, but I must be not understanding something vital or prerequisite to this.
While I find all your answers to other questions extremely valuable, I'd appreciate if the answer would point me to the reference that I'm missing, so I can understand the problem, rather than just copy/paste the fixed code.

The main problem is that you're trying to connect to a new instance of DockWidgetContents, which gets also immediately deleted as soon as start() returns.
That new instance is obviously useless, as one already exists, but you have no direct ways to get it, because you create all classes "on the fly" when you add widgets to layouts and parents.
Remember that, while creating "instances on the fly" is not technically a problem, it doesn't allow you to keep references to those instances.
You have to create appropriate references to widgets and correctly connect them.
Here you can see the modifications required:
class MainWindowClass(QMainWindow):
def __init__(self):
super().__init__()
self.init_UI()
self.TheDockWidget()
self.mainWidget.topLeftWidget.signal.connect(
self.dockWidgetContents._add_item)
def init_UI(self):
self.setGeometry(100, 100, 400, 200)
self.setWindowTitle("Test App")
self.mainWidget = MainWidgetClass()
self.setCentralWidget(self.mainWidget)
def TheDockWidget(self):
self.dockWidget = QDockWidget('Status:')
self.dockWidget.setFeatures(QDockWidget.DockWidgetMovable | QDockWidget.DockWidgetFloatable)
self.addDockWidget(Qt.RightDockWidgetArea, self.dockWidget)
self.dockWidget.setSizePolicy(QSizePolicy(QSizePolicy.Minimum, QSizePolicy.Minimum))
self.dockWidgetContents = DockWidgetContents()
self.dockWidget.setWidget(self.dockWidgetContents)
class MainWidgetClass(QWidget):
def __init__(self):
super().__init__()
self.init_UI()
def init_UI(self):
mainLayout = QGridLayout()
self.setLayout(mainLayout)
self.topLeftWidget = TopLeftWidgetClass()
mainLayout.addWidget(self.topLeftWidget, 0, 0)

Use a variable/data in two tabs in PyQt5 / Python

I am trying to get input from a user in one tab then show it in the second tab. I could not find a question or an example about how to do that. This is an example of the code that I want to use, How can I show the data from Tab(1) Qlabel in QTextEdit box in Tab(2), I am a beginner in pyqt5 and not sure how this would work:
import sys
from PyQt5.QtWidgets import *
from PyQt5.QtCore import *
class TabWidget(QDialog):
def __init__(self):
super().__init__()
self.setWindowTitle('Tab Widget Application')
tabwidget = QTabWidget()
tabwidget.addTab(FirstTab(), 'First Tab')
tabwidget.addTab(SecondTab(),'Second Tab')
vbox=QVBoxLayout()
vbox.addWidget(tabwidget)
self.setLayout(vbox)
class FirstTab(QWidget):
def __init__(self):
super().__init__()
self.nameLabel = QLabel(self)
self.nameLabel.setText('Name:')
self.line = QLineEdit(self)
self.line.move(80, 20)
self.line.resize(200, 32)
self.nameLabel.move(20, 20)
self.btn=QPushButton('switch',self)
self.btn.move(80, 50)
self.btn.clicked.connect(lambda: SecondTab.display(SecondTab(),self.nameLabel.text()))
class SecondTab(QWidget):
def __init__(self):
super().__init__()
self.layout = QVBoxLayout()
self.editor=QTextEdit()
self.layout.addWidget(self.editor)
self.setLayout(self.layout)
def display(self,text):
self.editor.setText(text)
if __name__ == '__main__':
app=QApplication(sys.argv)
tabwidget = TabWidget()
tabwidget.resize(500,500)
tabwidget.show()
app.exec()

In order to track changes amongst child widgets, you'll need a main "controller".
Your QTabWidget will suffice, as long as you implement it in the correct way:
class TabWidget(QDialog):
def __init__(self):
super().__init__()
self.setWindowTitle('Tab Widget Application')
# if the target widget of the layout is provided as an init argument, the
# layout will be automatically set to it
vbox = QVBoxLayout(self)
tabwidget = QTabWidget()
vbox.addWidget(tabwidget)
firstTab = FirstTab()
tabwidget.addTab(firstTab, 'First Tab')
secondTab = SecondTab()
tabwidget.addTab(secondTab,'Second Tab')
firstTab.line.textChanged.connect(secondTab.editor.setPlainText)
firstTab.btn.clicked.connect(lambda: tabwidget.setCurrentWidget(secondTab))

PyQT Button click doesn't work

So my problem is that instead of manually writing a ton of code for a bunch of buttons, I want to create a class for a QPushButton and then change so many variables upon calling that class to create my individual buttons.
My problem is that my button does not seem to be clickable despite calling the clicked.connect function and having no errors upon running the code. Here are the relevant parts of the button class:
class Button(QtGui.QPushButton):
def __init__(self, parent):
super(Button, self).__init__(parent)
self.setAcceptDrops(True)
self.setGeometry(QtCore.QRect(90, 90, 61, 51))
self.setText("Change Me!")
def retranslateUi(self, Form):
self.clicked.connect(self.printSomething)
def printSomething(self):
print "Hello"
Here is how I call the button class:
class MyWindow(QtGui.QWidget):
def __init__(self):
super(MyWindow,self).__init__()
self.btn = Button(self)
layout = QtGui.QVBoxLayout(self)
layout.addWidget(self.btn)
self.setLayout(layout)

You should perform the connection to the clicked signal on the __init__ method:
from PyQt4 import QtGui,QtCore
class Button(QtGui.QPushButton):
def __init__(self, parent):
super(Button, self).__init__(parent)
self.setAcceptDrops(True)
self.setGeometry(QtCore.QRect(90, 90, 61, 51))
self.setText("Change Me!")
self.clicked.connect(self.printSomething) #connect here!
#no need for retranslateUi in your code example
def printSomething(self):
print "Hello"
class MyWindow(QtGui.QWidget):
def __init__(self):
super(MyWindow,self).__init__()
self.btn = Button(self)
layout = QtGui.QVBoxLayout(self)
layout.addWidget(self.btn)
self.setLayout(layout)
app = QtGui.QApplication([])
w = MyWindow()
w.show()
app.exec_()
You can run it and will see the Hello printed on the console every time you click the button.
The retranslateUi method is for i18n. You can check here.

How to access variables from one class to another class in PyQt4?

I want to get a string from the main window to use in a window triggered with a click. I know how to do it by putting all statements into a single class, but now I'm trying to do the same thing with one class per window. Here is the code:
import sys
from PyQt4 import QtGui
class Window(QtGui.QWidget):
def __init__(self, parent=None):
super().__init__()
self.initUI()
def initUI(self):
self.value = QtGui.QLineEdit('23')
self.button = QtGui.QPushButton('Open Dialog')
self.button.clicked.connect(self.openDialog)
vbox = QtGui.QVBoxLayout()
vbox.addWidget(self.value)
vbox.addWidget(self.button)
self.setLayout(vbox)
def openDialog(self):
self.entry = self.value.text()
print(self.entry)
Dialog().exec_()
class Dialog(QtGui.QDialog):
def __init__(self, parent=Window):
super().__init__()
win = Window()
self.text = win.entry
self.label = QtGui.QLabel(self.text)
hbox = QtGui.QHBoxLayout()
hbox.addWidget(self.label)
self.setLayout(hbox)
def main():
app = QtGui.QApplication(sys.argv)
w = Window()
w.show()
sys.exit(app.exec_())
if __name__ == '__main__':
main()
But I'm getting the error "AttributeError: 'Window' object has no attribute 'entry'" and I don't know any other way to try fix it. Can someone help me with it?

Create an instance of Dialog in the openDialog method, so that you can access its attributes directly. That way, the two classes can operate more independently, and you won't need to access the Window class from within the Dialog class:
def openDialog(self):
dialog = Dialog(self)
dialog.label.setText(self.value.text())
dialog.exec_()
print(dialog.label.text())
class Dialog(QtGui.QDialog):
def __init__(self, parent=None):
super().__init__(parent)
self.label = QtGui.QLabel(self)
hbox = QtGui.QHBoxLayout()
hbox.addWidget(self.label)
self.setLayout(hbox)

Here
win = Window()
self.text = win.entry
you declare a new window and accesing its entry field but on your window class
class Window(QtGui.QWidget):
def __init__(self, parent=None):
super().__init__()
self.initUI()
the entry field is not constructed.
So
Either you want to create a new window, so you have to put the self.entry on the constructor
You want to use the existing window an access its entry after calling openDialog
Edit:
Maybe here
class Dialog(QtGui.QDialog):
def __init__(self, parent=Window):
super().__init__()
you are initializing the class wrong. The parent constructor should be called with parent=Window too. Then from inside the dialog you could reference the window by doing self.parent

Creating a button for PyQT window at each loop

class Test(QtGui.QMainWindow):
def __init__(self):
super(Test, self).__init__()
self.initUI()
def initUI(self):
YDrive = QtGui.QAction(QtGui.QIcon('y.gif'), 'Exit', self)
SDrive = QtGui.QAction('S', self)
GDrive = QtGui.QAction('G', self)
AddDrive = QtGui.QAction('+', self)
YDrive.triggered.connect(self.setYDir)
SDrive.triggered.connect(self.setSDir)
GDrive.triggered.connect(self.setGDir)
self.toolbar = self.addToolBar('Exit')
self.toolbar.addAction(YDrive)
self.toolbar.addAction(SDrive)
self.toolbar.addAction(GDrive)
self.toolbar.addAction(AddDrive)
#btn1 = QtGui.QPushButton("Button 1", self)
#btn1.move(30, 50)
#btn2 = QtGui.QPushButton("Button 2", self)
#btn2.move(150, 50)
#btn1.clicked.connect(self.buttonClicked)
#btn2.clicked.connect(self.buttonClicked)
self.setGeometry(300, 300, 250, 150)
self.center()
self.setWindowTitle('Message box')
self.show()
def setYDir(self):
myInputs[1] = "Y"
print "myInputs[1] CHANGED to Y"
myWorkDrive = "Y:\\HoC_Jobs\\"
shows = self.listDirs(myWorkDrive)
for elements in shows:
btn1 = QtGui.QPushButton(elements, self)
btn1.move(30, 50)
btn1.clicked.connect(self.buttonClicked)
What I'm trying to do in the last loop in setYDir is create a button for each element in the list shows. However, it doesn't seem to be working right. It does not update the buttons depending on thebutton I click in the toolbar. Any help?

Well, if you add components to a parent widget without using a layout and after you've called show on the parent, you'll have to show the children yourself.
Also, all your buttons are overlapping, so you'll only see the last one added. When posting source it's always good to strip it down to the minimum required to run it. In this case that would look something like this:
from PyQt4 import QtGui
import os
class Test(QtGui.QMainWindow):
def __init__(self):
super(Test, self).__init__()
self.initUI()
def initUI(self):
YDrive = QtGui.QAction("Y", self)
YDrive.triggered.connect(self.setYDir)
self.toolbar = self.addToolBar('Exit')
self.toolbar.addAction(YDrive)
self.setGeometry(300, 300, 250, 150)
self.setWindowTitle('Message box')
self.show()
def buttonClicked(self):
print "clicked"
def setYDir(self):
myWorkDrive = "/tmp"
shows = os.listdir(myWorkDrive)
i = 0
for elements in shows:
btn1 = QtGui.QPushButton(elements, self)
btn1.move(30, 50 + i)
i += 30
btn1.clicked.connect(self.buttonClicked)
btn1.show()
self.resize(self.width(), 50 + i)
if __name__ == '__main__':
app = QtGui.QApplication([])
t = Test()
t.show()
app.exec_()