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How to have two widgets in one Main window

I am trying the whole morning already to fix that.
So I have a PyQt Main Window where I want to display two widgets.
In the first widget there are articles listed (which works so far).
When I click on them until now a QMessageBox is opening, but I want that
a second widget is opening where I can read the RSS Feed.
But this is not working. See Code below:
class ArticleWidgets(QWidget):
def __init__(self, *args):
super().__init__(*args)
self.setGeometry(610, 610, 600, 600)
self.initUi()
def initUi(self):
self.box = QHBoxLayout(self)
def show(self, feed=None):
self.title = QLabel()
self.summary = QLabel()
self.link = QLabel()
if feed:
self.title.setText(feed[0])
self.summary.setText(feed[1])
self.link.setText(feed[2])
self.box.addWidget(self.title)
self.box.addWidget(self.summary)
self.box.addWidget(self.link)
self.setLayout(self.box)
class TitleWidgets(QWidget):
def __init__(self, *args):
super().__init__(*args)
self.setGeometry(10, 10, 600, 600)
self.initUi()
def initUi(self):
vbox = QHBoxLayout(self)
self.titleList = QListWidget()
self.titleList.itemDoubleClicked.connect(self.onClicked)
self.titleList.setGeometry(0, 0, 400, 400)
self.news = ANFFeed()
for item in self.news.all_feeds:
self.titleList.addItem(item[0])
vbox.addWidget(self.titleList)
def onClicked(self, item):
feeds = self.news.all_feeds
id = 0
for elem in range(len(feeds)):
if feeds[elem][0] == item.text():
id = elem
summary = feeds[id][1] + '\n\n'
link = feeds[id][2]
if feeds and id:
#ANFApp(self).show_articles(feeds[id])
show = ANFApp()
show.show_articles(feed=feeds[id])
QMessageBox.information(self, 'Details', summary + link)
class ANFApp(QMainWindow):
def __init__(self, *args):
super().__init__(*args)
self.setWindowState(Qt.WindowMaximized)
self.setWindowIcon(QIcon('anf.png'))
self.setAutoFillBackground(True)
self.anfInit()
self.show()
def anfInit(self):
self.setWindowTitle('ANF RSS Reader')
TitleWidgets(self)
#article_box = ArticleWidgets(self)
exitBtn = QPushButton(self)
exitBtn.setGeometry(600, 600, 100, 50)
exitBtn.setText('Exit')
exitBtn.setStyleSheet("background-color: red")
exitBtn.clicked.connect(self.exit)
def show_articles(self, feed=None):
present = ArticleWidgets()
present.show(feed)
def exit(self):
QCoreApplication.instance().quit()

Solution using Pyqtgraph's Docks and QTextBrowser
Here is a code trying to reproduce your sketch. I used the Pyqtgraph module (Documentation here: Pyqtgraph's Documentation and Pyqtgraph's Web Page) because its Dock widget is easier to use and implement from my perspective.
You must install the pyqtgraph module before trying this code:
import sys
from PyQt5 import QtGui, QtCore
from pyqtgraph.dockarea import *
class DockArea(DockArea):
## This is to prevent the Dock from being resized to te point of disappear
def makeContainer(self, typ):
new = super(DockArea, self).makeContainer(typ)
new.setChildrenCollapsible(False)
return new
class MyApp(QtGui.QMainWindow):
def __init__(self):
QtGui.QMainWindow.__init__(self)
central_widget = QtGui.QWidget()
layout = QtGui.QVBoxLayout()
central_widget.setLayout(layout)
self.setCentralWidget(central_widget)
label = QtGui.QLabel('This is a label, The widgets will be below')
label.setMaximumHeight(15)
## The DockArea as its name says, is the are where we place the Docks
dock_area = DockArea(self)
## Create the Docks and change some esthetic of them
self.dock1 = Dock('Widget 1', size=(300, 500))
self.dock2 = Dock('Widget 2', size=(400, 500))
self.dock1.hideTitleBar()
self.dock2.hideTitleBar()
self.dock1.nStyle = """
Dock > QWidget {
border: 0px solid #000;
border-radius: 0px;
}"""
self.dock2.nStyle = """
Dock > QWidget {
border: 0px solid #000;
border-radius: 0px;
}"""
self.button = QtGui.QPushButton('Exit')
self.widget_one = WidgetOne()
self.widget_two = WidgetTwo()
## Place the Docks inside the DockArea
dock_area.addDock(self.dock1)
dock_area.addDock(self.dock2, 'right', self.dock1)
## The statment above means that dock2 will be placed at the right of dock 1
layout.addWidget(label)
layout.addWidget(dock_area)
layout.addWidget(self.button)
## Add the Widgets inside each dock
self.dock1.addWidget(self.widget_one)
self.dock2.addWidget(self.widget_two)
## This is for set the initial size and posotion of the main window
self.setGeometry(100, 100, 600, 400)
## Connect the actions to functions, there is a default function called close()
self.widget_one.TitleClicked.connect(self.dob_click)
self.button.clicked.connect(self.close)
def dob_click(self, feed):
self.widget_two.text_box.clear()
## May look messy but wat i am doing is somethin like this:
## 'Title : ' + feed[0] + '\n\n' + 'Summary : ' + feed[1]
self.widget_two.text_box.setText(
'Title : ' + feed[0]\
+ '\n\n' +\
'Summary : ' + feed[1]
)
class WidgetOne(QtGui.QWidget):
## This signal is created to pass a "list" when it (the signal) is emited
TitleClicked = QtCore.pyqtSignal([list])
def __init__(self):
QtGui.QWidget.__init__(self)
self.layout = QtGui.QVBoxLayout()
self.setLayout(self.layout)
self.titleList = QtGui.QListWidget()
self.label = QtGui.QLabel('Here is my list:')
self.layout.addWidget(self.label)
self.layout.addWidget(self.titleList)
self.titleList.addItem(QtGui.QListWidgetItem('Title 1'))
self.titleList.addItem(QtGui.QListWidgetItem('Title 2'))
self.titleList.itemDoubleClicked.connect(self.onClicked)
def onClicked(self, item):
## Just test values
title = item.text()
summary = "Here you will put the summary of {}. ".format(title)*50
## Pass the values as a list in the signal. You can pass as much values
## as you want, remember that all of them have to be inside one list
self.TitleClicked.emit([title, summary])
class WidgetTwo(QtGui.QWidget):
def __init__(self):
QtGui.QWidget.__init__(self)
self.layout = QtGui.QVBoxLayout()
self.setLayout(self.layout)
self.label2 = QtGui.QLabel('Here we show results?:')
self.text_box = QtGui.QTextBrowser()
self.layout.addWidget(self.label2)
self.layout.addWidget(self.text_box)
if __name__ == "__main__":
app = QtGui.QApplication(sys.argv)
window = MyApp()
window.show()
sys.exit(app.exec_())
Again, there are comments inside the code to help you understand what I did.
Here is how it looks:
If you pass the mouse between the two widgets you will see the mouse icon will change, with that you can readjust on the run the size of both widgets.
Final Words
This is another approach, more "interactive" and more esthetic than my previous answer. As you said, using a QSplitter works too.

Problems
The way you are building your GUI is, in my opinion, messy and it may lead to errors. I suggest the use of Layouts for a more organized GUI.
The other problem is that each widget is an independent class so if you want to connect an action in one widget to do something in the other widget through the Main Window, you must use Signals.
Edit : Another suggestion, use other name for the close function instead of exit and try using self.close() instead of QCoreApplication.instance().quit()
Solution
Trying to emulate what you want to do I made this GUI:
import sys
from PyQt5 import QtGui, QtCore
class MyWindow(QtGui.QMainWindow):
def __init__(self):
QtGui.QMainWindow.__init__(self)
## Generate the structure parts of the MainWindow
self.central_widget = QtGui.QWidget() # A QWidget to work as Central Widget
self.layout1 = QtGui.QVBoxLayout() # Vertical Layout
self.layout2 = QtGui.QHBoxLayout() # Horizontal Layout
self.widget_one = WidgetOne()
self.widget_two = WidgetTwo()
self.exitBtn = QtGui.QPushButton('Exit')
## Build the structure
# Insert a QWidget as a central widget for the MainWindow
self.setCentralWidget(self.central_widget)
# Add a principal layout for the widgets/layouts you want to add
self.central_widget.setLayout(self.layout1)
# Add widgets/layuts, as many as you want, remember they are in a Vertical
# layout: they will be added one below of the other
self.layout1.addLayout(self.layout2)
self.layout1.addWidget(self.exitBtn)
# Here we add the widgets to the horizontal layout: one next to the other
self.layout2.addWidget(self.widget_one)
self.layout2.addWidget(self.widget_two)
## Connect the signal
self.widget_one.TitleClicked.connect(self.dob_click)
def dob_click(self, feed):
## Change the properties of the elements in the second widget
self.widget_two.title.setText('Title : '+feed[0])
self.widget_two.summary.setText('Summary : '+feed[1])
## Build your widgets same as the Main Window, with the excepton that here you don't
## need a central widget, because it is already a widget.
class WidgetOne(QtGui.QWidget):
TitleClicked = QtCore.pyqtSignal([list]) # Signal Created
def __init__(self):
QtGui.QWidget.__init__(self)
##
self.layout = QtGui.QVBoxLayout() # Vertical Layout
self.setLayout(self.layout)
self.titleList = QtGui.QListWidget()
self.label = QtGui.QLabel('Here is my list:')
self.layout.addWidget(self.label)
self.layout.addWidget(self.titleList)
self.titleList.addItem(QtGui.QListWidgetItem('Title 1'))
self.titleList.addItem(QtGui.QListWidgetItem('Title 2'))
self.titleList.itemDoubleClicked.connect(self.onClicked)
def onClicked(self, item):
## Just test parameters and signal emited
self.TitleClicked.emit([item.text(), item.text()+item.text()])
class WidgetTwo(QtGui.QWidget):
def __init__(self):
QtGui.QWidget.__init__(self)
self.layout = QtGui.QVBoxLayout()
self.setLayout(self.layout)
self.title = QtGui.QLabel('Title : ---')
self.summary = QtGui.QLabel('Summary : ---')
self.link = QtGui.QLabel('Link : ---')
self.layout.addWidget(self.title)
self.layout.addWidget(self.summary)
self.layout.addWidget(self.link)
if __name__ == "__main__":
app = QtGui.QApplication(sys.argv)
window = MyWindow()
window.show()
sys.exit(app.exec_())
Inside the code, there are comments to help you understand why I did to build an organized GUI. There is also an example of a Signal being used to connect the action of itemDoubleClicked from the first widget to the second one. Here is how the MainWindow looks:
It is not very clear how the layouts work just from seeing the result, so I did a little paint over to a better understanding:
The blue box is the vertical layout (QVBoxLayout) and the red one is the horizontal layout (QHBoxLayout). Inside the blue layout, are located the red layout (above) and the exit button (below); and inside the red layout, are located the widget_1 (left) and the widget_2 (right).
Other Solution
An "easier" solution will be building the widgets inside the MainWindow instead of creating separate classes. With this you will avoid the use of signals, but the code will become a little more confusing because all the code will be cramped in one class.

How to align QLineEdits within a QWidget?

I have a widget which contains three labels and three lineedits. I would like all lineedits to be aligned vertically directly after the longest label.
Here is my class:
class ScaleDisplayWidget(QWidget):
def __init__(self, parent=None):
super(ScaleDisplayWidget, self).__init__(parent)
self.setFixedSize(400, 200)
self.initUI()
self.update(0, 0, 0)
def initUI(self):
'''
Setup GUI elements of scale window
'''
mainLayout = QVBoxLayout()
hLayout = QHBoxLayout()
hLayout.setSpacing(0)
self.dx_label = QLabel('DX:')
self.dx_label.setFixedWidth(80)
self.dx_edit = QLineEdit()
self.dx_edit.setReadOnly(True)
self.dx_edit.setFocus(True)
self.dx_edit.setFixedWidth(150)
hLayout.addWidget(self.dx_label)
hLayout.addWidget(self.dx_edit)
h2Layout = QHBoxLayout()
h2Layout.setSpacing(0)
self.dy_label = QLabel('DY:')
self.dy_label.setFixedWidth(80)
self.dy_edit = QLineEdit()
self.dy_edit.setReadOnly(True)
self.dy_edit.setFocus(True)
self.dy_edit.setFixedWidth(150)
h2Layout.addWidget(self.dy_label)
h2Layout.addWidget(self.dy_edit)
h3Layout = QHBoxLayout()
h3Layout.setSpacing(0)
self.dist_label = QLabel('Distance:')
self.dist_label.setFixedWidth(80)
self.dist_edit = QLineEdit()
self.dist_edit.setReadOnly(True)
self.dist_edit.setFocus(True)
self.dist_edit.setFixedWidth(150)
h3Layout.addWidget(self.dist_label)
h3Layout.addWidget(self.dist_edit)
mainLayout.addLayout(hLayout)
mainLayout.addLayout(h2Layout)
mainLayout.addLayout(h3Layout)
self.setLayout(mainLayout)
self.show()
def update(self, dx, dy, dist):
self.dx_edit.setText(str(dx))
self.dy_edit.setText(str(dy))
self.dist_edit.setText(str(dist))
In this case I'm aiming to have all lineedits aligned directly after the distance label (maybe add 5 pixels or something small of padding). I have tried using setContentsMargins(0,0,0,0) on all the layouts but it hasn't changed anything.

Use a QFormLayout instead:
self.dx_edit = QLineEdit()
self.dx_edit.setReadOnly(True)
self.dx_edit.setFocus(True)
self.dx_edit.setFixedWidth(150)
self.dy_edit = QLineEdit()
self.dy_edit.setReadOnly(True)
self.dy_edit.setFocus(True)
self.dy_edit.setFixedWidth(150)
self.dist_edit = QLineEdit()
self.dist_edit.setReadOnly(True)
self.dist_edit.setFocus(True)
self.dist_edit.setFixedWidth(150)
layout = QFormLayout(self)
layout.addRow("DX", self.dx_edit)
layout.addRow("DY", self.dy_edit)
layout.addRow("Distance", self.dist_edit)
You might need to set the label align to left with layout.setLabelAlignment(Qt.AlignLeft)

How to open a QDialog window with a function passing args?

I'm in big trouble, I can't figure it out how to open my window "PlotWindow" with my "OpendPlotWindow" function. I'm new in PyQt so it is a dumb question, but I really don't understand what's wrong in my code
PlotWindow:
class PlotWindoW(QDialog):
def __init__(self,x,y, parent=None):
super(Window, self).__init__(parent)
self.figure = plt.figure()
self.canvas = FigureCanvas(self.figure)
self.toolbar = NavigationToolbar(self.canvas, self)
self.plot(x,y)
layout = QVBoxLayout()
layout.addWidget(self.toolbar)
layout.addWidget(self.canvas)
self.setLayout(layout)
self.show()
def plot(self,x,y):
self.figure.clear()
ax = self.figure.add_subplot(111)
ax.plot(x,y)
self.canvas.draw()
PlotSetting:
class PlotSetting(QWidget):
def __init__(self,fileNameFm,fileNameMesh,fileNameSmry,fileNameXY, parent=None):
super(QWidget, self).__init__(parent)
print("setting start")
donnees.fileFm=fileNameFm
donnees.fileMesh=fileNameMesh
donnees.fileSmry=fileNameSmry
donnees.fileXY=fileNameXY
self.layout = QVBoxLayout(self)
self.tabs = QTabWidget()
self.tab1 = QWidget()
self.tabs.sizeHint()
self.tabs.addTab(self.tab1,"Setting Mesh")
LabelFm = QLabel(donnees.fileFm)
LabelMesh = QLabel(donnees.fileMesh)
btnNe=QPushButton("Choose Ne", self)
btnNe.clicked.connect(self.getInteger)
FmPlotBtn=QPushButton("Plot Mesh File", self)
FmPlotBtn.clicked.connect(self.GetDataFm)
self.tab1.layout = QVBoxLayout(self)
self.tab1.layout.addWidget(LabelFm)
self.tab1.layout.addWidget(LabelMesh)
self.tab1.layout.addWidget(btnNe)
self.tab1.layout.addWidget(FmPlotBtn)
self.tab1.setLayout(self.tab1.layout)
self.layout.addWidget(self.tabs)
self.setLayout(self.layout)
def getInteger(self):
donnees.Ne, okPressed = QInputDialog.getInt(self, "Get integer","Ne:", 66, 66, 98, 2)
if okPressed:
print(donnees.Ne)
def GetDataFm(self):
print('plot start')
data = {}
data = Fm( donnees.fileFm , donnees.fileMesh )
x,y=PloterFm(data,donnees.Ne)
print(x[0],y[0])
self.OpenPlotWindow(x,y)
def OpenPlotWindow(self, x, y):
print("OpenPlotWIndow is running")
print(x[0],y[0])
self.ThirdWindow = PlotWindoW(x,y)
self.ThirdWindow.show()
The problem: when I run my code, it comes to OpenPlotWindow which get all data needed, but it never enter into PlotWindow...
Please can you help me?

As per the docs for QPushButton's super class QAbstractButton, clicked takes one argument, bool checked = false. It's actually pretty useless on QPushButton as far as I've seen, but nevertheless, your function needs to account for this. Try this line instead
def GetDataFm(self, clicked=False):
....

All the widgets disappear when window size is decreased

When I decrease the window size all the widgets disappear.I want the widgets to move along when size is decreased.How do I solve this problem?
I have a drop-down menu from which a value is selected.When an "Add cmd" button is pressed the value is added to edit box.
Thanks in advance.
import sys
from PyQt4.QtCore import *
from PyQt4.QtGui import *
class tabdemo(QTabWidget):
def __init__(self, parent = None):
super(tabdemo, self).__init__(parent)
self.setGeometry(50, 50, 400,400)
QShortcut(QKeySequence("Esc"), self, self.close)
self.tab1 = QWidget()
self.tab2 = QWidget()
self.addTab(self.tab1,"Tab 1")
self.tab1UI()
self.setWindowTitle("Main Window")
def tab1UI(self):
self.comboBox = QComboBox(self.tab1)
self.comboBox.addItem('ABC')
self.comboBox.addItem('BCD')
self.comboBox.addItem('CDE')
self.comboBox.move(5,20)
self.comboBox.resize(180,30)
self.button = QPushButton('Add Cmd', self.tab1)
self.button.move(190,20)
self.button.resize(80,30)
self.button.clicked.connect(self.handleTest)
self.b = QTextEdit(self.tab1)
self.b.move(20,75)
self.b.resize(290,200)
self.button = QPushButton('Send Batch', self.tab1)
self.button.move(40,300)
self.button.resize(150,30)
self.button = QPushButton('Clear', self.tab1)
self.button.move(200,300)
self.button.resize(80,30)
self.button.clicked.connect(self.deletevalue)
layout = QFormLayout()
self.setTabText(4,"BatchCMDS")
self.tab1.setLayout(layout)
def handleTest(self):
self.b.append(str(self.comboBox.currentText()))
def deletevalue(self):
self.b.clear()
def main():
app = QApplication(sys.argv)
ex = tabdemo()
ex.show()
sys.exit(app.exec_())
if __name__ == '__main__':
main()

If you want the widgets to adapt to the size of the window you should use layouts, For this, the application must be designed, for this an image is used of how you want your application to be:
As we see the widgets that are inside a tab are divided into 3 groups, the first is made up of the QComboBox with the QPushButton, the second the QTextEdit, and the third the 2 remaining buttons. Each group is horizontally distributed, so in that case we should use QHBoxLayout except the QTextEdit that is alone, and each group should be in QVBoxLayout. I do not understand why you use the QFormLayout, also if you use the layouts the positions are not necessary.
Another error that I see in your code is that several buttons have the same name, this causes errors like for example that the Add CMD button does not work, you must give a different name to each widget.
class tabdemo(QTabWidget):
def __init__(self, parent = None):
super(tabdemo, self).__init__(parent)
self.setGeometry(50, 50, 400,400)
QShortcut(QKeySequence("Esc"), self, self.close)
self.tab1 = QWidget()
self.tab2 = QWidget()
self.addTab(self.tab1,"Tab 1")
self.addTab(self.tab2,"Tab 2")
self.tab1UI()
def tab1UI(self):
vlayout = QVBoxLayout(self.tab1)
hlayout1 = QHBoxLayout()
self.comboBox = QComboBox(self.tab1)
self.comboBox.addItems(['ABC', 'BCD', 'CDE'])
self.button = QPushButton('Add Cmd', self.tab1)
self.button.clicked.connect(self.handleTest)
hlayout1.addWidget(self.comboBox)
hlayout1.addWidget(self.button)
hlayout1.addItem(QSpacerItem(100, 10, QSizePolicy.Expanding, QSizePolicy.Preferred))
vlayout.addLayout(hlayout1)
self.b = QTextEdit(self.tab1)
vlayout.addWidget(self.b)
hlayout2 = QHBoxLayout()
self.buttonSend = QPushButton('Send Batch', self.tab1)
self.buttonClear = QPushButton('Clear', self.tab1)
self.buttonClear.clicked.connect(self.deletevalue)
hlayout2.addItem(QSpacerItem(100, 10, QSizePolicy.Expanding, QSizePolicy.Preferred))
hlayout2.addWidget(self.buttonSend)
hlayout2.addWidget(self.buttonClear)
hlayout2.addItem(QSpacerItem(100, 10, QSizePolicy.Expanding, QSizePolicy.Preferred))
vlayout.addLayout(hlayout2)
self.setTabText(4,"BatchCMDS")
def handleTest(self):
self.b.append(self.comboBox.currentText())
def deletevalue(self):
self.b.clear()

PySide multi-window, get QStackWidget to work

I need to create multi-window GUI, first I tried it with QWidgets, but finally I discover QStackWidget tool I need to use. So Im trying to, but Ive got some problems. Thanks for Your time.
class MainWindow(QMainWindow):
def __init__(self):
super(MainWindow,self).__init__()
self.mainWidget = MainWidget()
self.searchWidget = SearchWidget()
self.sWidget = QStackedWidget()
self.sWidget.addWidget(self.mainWidget)
self.sWidget.addWidget(self.searchWidget)
self.initUI()
and calling setCurrentWidget from the sub_widget class:
class MainWidget(QWidget):
def __init__(self, parent=MainWindow):
super(MainWidget,self).__init__()
self.initUI()
def initUI(self):
searchButton = QPushButton('searchButton',self)
optionButton = QPushButton('optionButton',self)
quitButton = QPushButton('quitButton',self)
listButton = QPushButton('listButton',self)
searchButton.clicked.connect(self.goSearch)
hbox = QHBoxLayout()
hbox.addWidget(listButton)
hbox.addWidget(quitButton)
vbox = QVBoxLayout()
vbox.addStretch(1)
vbox.addWidget(searchButton)
vbox.addWidget(optionButton)
vbox.addLayout(hbox)
self.setLayout(vbox)
def goSearch(self):
self.parent().sWidget.setCurrentWidget(self.parent().searchWidget)
Ive got this message from IDE:
self.parent().sWidget.setCurrentWidget(self.parent().searchWidget)
AttributeError: 'PySide.QtGui.QStackedWidget' object has no attribute 'sWidget'
What is the thing Im doing wrong?

I'm going to comment on the code you posted here: http://pastebin.com/fBfS1X5m
An important thing to know is that you can put widgets within widgets and so on. For example:
class Widget(QWidget):
def __init__(self, parent=None):
layout = QVBoxLayout(self)
childWidget = QWidget(parent=self)
layout.addWidget(childWidget)
Just a quick note: You don't need setLayout if you pass self to the main layout constructor - via the docs.
Anyways, what I'm trying to illustrate here is that the QStackedWidget and the SearchWidget really shouldn't be a part of the MainWindow, but should live inside their own relevant widget that will handle switching between the QStackedWidget pages.
For example the MainWindow.__init__ would only look like this:
class MainWindow(QMainWindow):
def __init__(self):
super(MainWindow, self).__init__()
self.mainWidget = MainWidget(self)
self.setCentralWidget(self.mainWidget)
self.initUI()
Your MainWidget would then look something like:
class MainWidget(QtGui.QWidget):
...
def initUI(self):
...
self.stack = QtGui.QStackedWidget(parent=self)
self.searchWidget = SearchWidget(parent=self)
self.searchWidget.searchButton.clicked.connect(self.goSearch)
self.backWidget = BackWidget(parent=self)
self.backWidget.backButton.clicked.connect(self.goBack)
...
def goSearch(self):
self.stack.setCurrentWidget(self.backWidget)
def goBack(self):
self.stack.setCurrentWidget(self.searchWidget)
I've renamed some of the class names to make a little more sense (To me at least). SearchWidget was your old MainWidget. BackWidget was your old SearchWidget. Following those changes SearchWidget would look the same as your old MainWidget with one exception - we save a reference to the search button so we can access it in the MainWidget class as seen above (when we connect their signals to our slots). We do the same for the button in BackWidget.
The two renamed "child" widgets:
class SearchWidget(QtGui.QWidget):
...
def initUI(self):
self.searchButton = QtGui.QPushButton('searchButton', parent=self)
optionButton = QtGui.QPushButton('optionButton', parent=self)
quitButton = QtGui.QPushButton('quitButton', parent=self)
listButton = QtGui.QPushButton('listButton', parent=self)
vbox = QtGui.QVBoxLayout(self)
vbox.addStretch(1)
vbox.addWidget(self.searchButton)
vbox.addWidget(optionButton)
hbox = QtGui.QHBoxLayout()
hbox.addWidget(listButton)
hbox.addWidget(quitButton)
vbox.addLayout(hbox)
class BackWidget(QtGui.QWidget):
...
def initUI(self):
self.backButton = QtGui.QPushButton('GoBack', parent=self)
So now we have something like:
MainWindow
|---MainWidget
|---QStackedWidget
|---SearchWidget
|---BackWidget
You can find the full working code here.

This line:
def __init__(self, parent=MainWindow):
sets the MainWindow class as a default argument, when you actually need an instance. But even if it was an instance, in the next line, you also fail to pass it on to the base-class:
super(MainWidget,self).__init__()
What you need to do instead is something like this:
class MainWindow(QMainWindow):
def __init__(self):
super(MainWindow,self).__init__()
# pass an instance of MainWindow here
self.mainWidget = MainWidget(self)
...
class MainWidget(QWidget):
def __init__(self, parent):
# pass the parent to the base-class
super(MainWidget, self).__init__(parent)
...
UPDATE:
The stack-widget will re-parent any widgets added to it, so that it becomes the parent. There are ways of working around this, but I think the real problem with your code is that you have the structure backwards. The buttons that set the current widget should be controlled by the main-window, and the widgets in the stack should work completely independantly of that.