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What is the difference between QLayout's setAlignment(QWidget, Alignment), setAlginment(QLayout, Alignment) and setAlginment(Alignment)? (PyQt5)

In the following code:
import sys
from PyQt5 import QtWidgets
from PyQt5.QtCore import Qt
from PyQt5.QtWidgets import QApplication, QWidget, QHBoxLayout, QTableWidget, QPushButton
class Window(QtWidgets.QMainWindow):
def __init__(self, method):
super(Window, self).__init__()
mainWidget = QWidget()
mainLayout = QHBoxLayout(mainWidget)
table = QTableWidget(10, 3)
button1 = QPushButton("Play")
button2 = QPushButton("Cancel")
mainLayout.addWidget(table)
mainLayout.addWidget(button1)
mainLayout.addWidget(button2)
if (method == 1):
rtnValue = mainLayout.setAlignment(button1, Qt.AlignTop)
print("Method 1:", rtnValue)
elif (method == 2):
rtnValue = mainLayout.setAlignment(mainLayout, Qt.AlignTop)
print("Method 2:", rtnValue)
else:
rtnValue = mainLayout.setAlignment(Qt.AlignTop)
print("Method X:", rtnValue)
self.setCentralWidget(mainWidget)
self.show()
if __name__ == "__main__":
print("python QLayoutAlignment.py[ <MethodToUse=1>")
app = QApplication(sys.argv)
method = 1 if (len(sys.argv) < 2) else int(sys.argv[1])
GUI = Window(method)
sys.exit(app.exec_())
when I call the program like below with mainLayout.setAlignment(button1, Qt.AlignTop) being called, it works as expected with the "Play" button aligned at the top and "Cancel" button aligned at the center vertically. I also found the documentation for bool QLayout::setAlignment(QWidget *w, Qt::Alignment alignment) although in Qt.
python QLayoutAlignment.py 1
However when I call the the program like below with mainLayout.setAlignment(mainLayout, Qt.AlignTop) being called, it does not seem to work. All the buttons are vertically center aligned. I interpreted the Qt documentation of bool QLayout::setAlignment(QLayout *l, Qt::Alignment alignment)) as "it align all the added widget of the layout to the set alignment". So what does this function actually do (when is it used)?
python QLayoutAlignment.py 2
Lastly, I also saw another example from Center and top align a QVBoxLayout. When I call the program like below with mainLayout.setAlignment(Qt.AlignTop) being called, it also does not work with all the buttons vertically center aligned. For this one I could not find its documentation. So what does this function actually do (when is it used) and where can I find its documentation?
python QLayoutAlignment.py 3

The .setAlignment method which accepts a layout is used for aligning sub-layouts, that is child layouts you've added to the parent layout using .addLayout.
Below is a little demo based on your code.
import sys
from PyQt5 import QtWidgets
from PyQt5.QtCore import Qt
from PyQt5.QtWidgets import QApplication, QWidget, QHBoxLayout, QTableWidget, QPushButton
class Window(QtWidgets.QMainWindow):
def __init__(self, method=0):
super(Window, self).__init__()
mainWidget = QWidget()
self.mainLayout = QHBoxLayout(mainWidget)
table = QTableWidget(10, 3)
self.button1 = QPushButton("Play")
self.button2 = QPushButton("Cancel")
self.subLayout = QHBoxLayout()
buttona1 = QPushButton("1")
buttona1.clicked.connect(self.clicked1)
buttona2 = QPushButton("2")
buttona2.clicked.connect(self.clicked2)
buttona3 = QPushButton("3")
buttona3.clicked.connect(self.clicked3)
buttona4 = QPushButton("4")
buttona4.clicked.connect(self.clicked4)
self.subLayout.addWidget(buttona1)
self.subLayout.addWidget(buttona2)
self.subLayout.addWidget(buttona3)
self.subLayout.addWidget(buttona4)
self.mainLayout.addWidget(table)
self.mainLayout.addWidget(self.button1)
self.mainLayout.addWidget(self.button2)
self.mainLayout.addLayout(self.subLayout)
self.setCentralWidget(mainWidget)
self.show()
def clicked1(self):
rtnValue = self.mainLayout.setAlignment(self.button1, Qt.AlignTop)
print("Method 1:", rtnValue)
def clicked2(self):
rtnValue = self.mainLayout.setAlignment(self.mainLayout, Qt.AlignTop)
print("Method 2:", rtnValue)
def clicked3(self):
rtnValue = self.mainLayout.setAlignment(Qt.AlignTop)
print("Method 3:", rtnValue)
def clicked4(self):
rtnValue = self.mainLayout.setAlignment(self.subLayout, Qt.AlignTop)
print("Method 4:", rtnValue)
if __name__ == "__main__":
print("python QLayoutAlignment.py[ <MethodToUse=1>")
app = QApplication(sys.argv)
method = 1 if (len(sys.argv) < 2) else int(sys.argv[1])
GUI = Window(method)
sys.exit(app.exec_())
You'll notice if you trigger this self.mainLayout.setAlignment(self.mainLayout, Qt.AlignTop) the return value is False. This is telling you that the layout you're aligning could not be found in the current layout. Since you're calling .setAlignment on mainLayout the layout you're affecting must be in that layout.
In the 4th method, I've added a sub-layout, and as you can see this ( rtnValue = self.mainLayout.setAlignment(self.subLayout, Qt.AlignTop)) works as expected and returns True.

First of all, it's important to understand that the Qt layout system works by using layout items (see QLayoutItem), which are abstract items that are used as virtual containers for objects: widgets, spacers and layouts (when nested layouts are used). Every QLayout is, in fact, a subclass of QLayoutItem.
Using setAlignment means setting the alignment of the specified layout item:
layout.setAlignment(item, alignment) sets the alignment of item, which has to be directly contained in layout;
layout.setAlignment(alignment) sets the alignment of layout related to its parent layout; note that this does not mean that items inside layout will use the specified alignment;
Your second case, mainLayout.setAlignment(mainLayout, Qt.AlignTop), does not work and returns False because mainLayout is, obviously, not "contained" in mainLayout. In fact, if you carefully read the documentation, it says:
returns true if w/l is found in this layout (not including child layouts);
In your third case, you don't see any result because mainLayout is the top layout for the widget, and since there's no parent layout the alignment seems to be ignored. As specified above, using layout.setAlignment(alignment) does not set the alignment of child items, but only of the layout item of layout. If you add that mainLayout to another layout, you will see that the alignment is respected for the layout.
Setting the layout alignment is rarely used, also because it's often counterintuitive: one might led to believe that setting the alignment of a layout will align its contents, but that's not the case.
To clarify, consider that setting the layout alignment is almost the same as creating a widget with that layout, and adding that widget with the specified alignment. With that in mind, it makes more sense: you're not aligning the contents of the widget, but the widget itself.
Consider the following example: besides the table on the left (used for comparison), I'm adding a layout on the left by specifying its alignment, then I'm adding a widget on the right by specifying the alignment of the widget for the main layout. As you can see, they appear exactly the same.
from PyQt5 import QtCore, QtWidgets
import sys
app = QtWidgets.QApplication(sys.argv)
test = QtWidgets.QWidget()
mainLayout = QtWidgets.QHBoxLayout(test)
# a very tall table to show the difference in alignment
mainLayout.addWidget(QtWidgets.QTableView(minimumHeight=300))
leftLayout = QtWidgets.QHBoxLayout()
# setting the alignment of leftLayout relative to mainLayout
leftLayout.setAlignment(QtCore.Qt.AlignTop)
leftLayout.addWidget(QtWidgets.QTableView(maximumHeight=100))
leftLayout.addWidget(QtWidgets.QPushButton())
mainLayout.addLayout(leftLayout)
rightWidget = QtWidgets.QWidget()
# adding the widget to mainLayout by aligning it on top as with leftLayout
mainLayout.addWidget(rightWidget, alignment=QtCore.Qt.AlignTop)
rightLayout = QtWidgets.QHBoxLayout(rightWidget)
rightLayout.addWidget(QtWidgets.QTableView(maximumHeight=100))
rightLayout.addWidget(QtWidgets.QPushButton())
test.show()
sys.exit(app.exec_())
Finally, if you want to align widgets, you either specify the alignment for each widget, or you add nested layout.
When many widgets are going to be added with the same alignment, the nested layout is usually the best solution: in your case, add a vertical layout to the main layout, then add horizontal layout to the vertical for the buttons, and add a stretch to the vertical to "push" the horizontal layout on top.
Alternatively, you can use a grid layout and eventually use spacers to ensure that the widgets are "aligned" as required.
from PyQt5 import QtCore, QtWidgets
import sys
app = QtWidgets.QApplication(sys.argv)
test = QtWidgets.QWidget()
mainLayout = QtWidgets.QHBoxLayout(test)
class Button(QtWidgets.QPushButton):
def __init__(self, *args, **kwargs):
super().__init__(*args, **kwargs)
self.setSizePolicy(
QtWidgets.QSizePolicy.Preferred,
QtWidgets.QSizePolicy.Preferred
)
noAlignGroup = QtWidgets.QGroupBox('no alignment')
mainLayout.addWidget(noAlignGroup)
noAlignLayout = QtWidgets.QHBoxLayout(noAlignGroup)
noAlignLayout.addWidget(QtWidgets.QTableView())
noAlignLayout.addWidget(Button())
noAlignLayout.addWidget(Button())
widgetAlignGroup = QtWidgets.QGroupBox('addWidget(widget, alignment)')
mainLayout.addWidget(widgetAlignGroup)
widgetAlignLayout = QtWidgets.QHBoxLayout(widgetAlignGroup)
widgetAlignLayout.addWidget(QtWidgets.QTableView())
widgetAlignLayout.addWidget(Button(), alignment=QtCore.Qt.AlignTop)
widgetAlignLayout.addWidget(Button(), alignment=QtCore.Qt.AlignTop)
layoutAlignGroup = QtWidgets.QGroupBox('nestedLayout.setAlignment()')
mainLayout.addWidget(layoutAlignGroup)
layoutAlignLayout = QtWidgets.QHBoxLayout(layoutAlignGroup)
layoutAlignLayout.addWidget(QtWidgets.QTableView())
buttonLayout = QtWidgets.QHBoxLayout()
layoutAlignLayout.addLayout(buttonLayout)
buttonLayout.setAlignment(QtCore.Qt.AlignTop)
buttonLayout.addWidget(Button())
buttonLayout.addWidget(Button())
stretchGroup = QtWidgets.QGroupBox('nestedLayout + stretch')
mainLayout.addWidget(stretchGroup)
stretchLayout = QtWidgets.QHBoxLayout(stretchGroup)
stretchLayout.addWidget(QtWidgets.QTableView())
rightLayout = QtWidgets.QVBoxLayout()
stretchLayout.addLayout(rightLayout)
buttonLayout = QtWidgets.QHBoxLayout()
rightLayout.addLayout(buttonLayout)
buttonLayout.addWidget(Button())
buttonLayout.addWidget(Button())
rightLayout.addStretch()
gridAlignGroup = QtWidgets.QGroupBox('grid + spacer')
mainLayout.addWidget(gridAlignGroup)
gridLayout = QtWidgets.QGridLayout(gridAlignGroup)
gridLayout.addWidget(QtWidgets.QTableView(), 0, 0, 2, 1)
gridLayout.addWidget(Button(), 0, 1)
gridLayout.addWidget(Button(), 0, 2)
spacer = QtWidgets.QSpacerItem(1, 50, vPolicy=QtWidgets.QSizePolicy.Expanding)
gridLayout.addItem(spacer, 1, 1)
test.show()
sys.exit(app.exec_())

PyQt5 removing button

In the list_widget I have added a add button I also want to add a remove button which asks which item you wants to remove and remove the chosen item. I was trying it to do but I didn't had any idea to do so .Also, please explain the solution I am a beginner with pyqt5 or I'd like to say absolute beginner.
from PyQt5 import QtWidgets
from PyQt5.QtWidgets import QApplication,QMainWindow,
QListWidget, QListWidgetItem
import sys
class MyWindow(QMainWindow):
def __init__(self):
super(MyWindow, self).__init__()
self.x = 200
self.y = 200
self.width = 500
self.length = 500
self.setGeometry(self.x, self.y, self.width,
self.length)
self.setWindowTitle("Stock managment")
self.iniTUI()
def iniTUI(self):
# buttons
self.b1 = QtWidgets.QPushButton(self)
self.b1.setText("+")
self.b1.move(450, 100)
self.b1.resize(50, 25)
self.b1.clicked.connect(self.take_inputs)
# This is the button I want to define.
self.btn_minus = QtWidgets.QPushButton(self)
self.btn_minus.setText("-")
self.btn_minus.move(0, 100)
self.btn_minus.resize(50, 25)
# list
self.list_widget = QListWidget(self)
self.list_widget.setGeometry(120, 100, 250, 300)
self.item1 = QListWidgetItem("A")
self.item2 = QListWidgetItem("B")
self.item3 = QListWidgetItem("C")
self.list_widget.addItem(self.item1)
self.list_widget.addItem(self.item2)
self.list_widget.addItem(self.item3)
self.list_widget.setCurrentItem(self.item2)
def take_inputs(self):
self.name, self.done1 =
QtWidgets.QInputDialog.getText(
self, 'Add Item to List', 'Enter The Item you want
in
the list:')
self.roll, self.done2 = QtWidgets.QInputDialog.getInt(
self, f'Quantity of {str(self.name)}', f'Enter
Quantity of {str(self.name)}:')
if self.done1 and self.done2:
self.item4 = QListWidgetItem(f"{str(self.name)}
Quantity{self.roll}")
self.list_widget.addItem(self.item4)
self.list_widget.setCurrentItem(self.item4)
def clicked(self):
self.label.setText("You clicked the button")
self.update()
def update(self):
self.label.adjustSize()
def clicked():
print("meow")
def window():
apk = QApplication(sys.argv)
win = MyWindow()
win.show()
sys.exit(apk.exec_())
window()

The core issue here is the lack of separation of the view and the data. This makes it very hard to reason about how to work with graphical elements. You will almost certainly want to follow the Model View Controller design paradigm https://en.wikipedia.org/wiki/Model%E2%80%93view%E2%80%93controller
which offers a systematic way to handle this separation.
Once you do so, it immediately becomes very straight forward how to proceed with the question: You essentially just have a list, and you either want to add a thing to this list, or remove one based on a selection.
I include an example here which happens to use the built-in classes QStringListModel and QListView in Qt5, but it is simple to write your own more specialized widgets and models. They all just use a simple signal to emit to the view that it needs to refresh the active information.
from PyQt5.QtWidgets import *
from PyQt5.QtCore import *
import sys
class StuffViewer(QMainWindow):
def __init__(self, model):
super().__init__()
self.setWindowTitle("Stock managment")
# 1: Use layouts.
hbox = QHBoxLayout()
widget = QWidget()
widget.setLayout(hbox)
self.setCentralWidget(widget)
# 2: Don't needlessly store things in "self"
vbox = QVBoxLayout()
add = QPushButton("+")
add.clicked.connect(self.add_new_stuff)
vbox.addWidget(add)
sub = QPushButton("-")
sub.clicked.connect(self.remove_selected_stuff)
vbox.addWidget(sub)
vbox.addStretch(1)
hbox.addLayout(vbox)
# 3: Separate the view of the data from the data itself. Use Model-View-Controller design to achieve this.
self.model = model
self.stuffview = QListView()
self.stuffview.setModel(self.model)
hbox.addWidget(self.stuffview)
def add_new_stuff(self):
new_stuff, success = QInputDialog.getText(self, 'Add stuff', 'Enter new stuff you want')
if success:
self.stuff.setStringList(self.stuff.stringList() + [new_stuff])
def remove_selected_stuff(self):
index = self.stuffview.currentIndex()
all_stuff = self.stuff.stringList()
del all_stuff[index.column()]
self.stuff.setStringList(all_stuff)
def window():
apk = QApplication(sys.argv)
# Data is clearly separated:
# 4: Never enumerate variables! Use lists!
stuff = QStringListModel(["Foo", "Bar", "Baz"])
# The graphical components is just how you interface with the data with the user!
win = StuffViewer(stuff)
win.show()
sys.exit(apk.exec_())
window()

Qaction Shortcut in extended contextmenu not triggered

I try to extend the contextmenu of a QLineEdit with an additional entry for replacing text. I can extend the contextmenu with .createStandardContextMenu(), which works fine. But when I try to add a shortcut with .setShortcut(QKeySequence(Qt.CTRL + Qt.Key_R)) it will not react on the key. Same with different keys, which I tried. In addition the shortcut made with QAction('&Replace', self) doesn't work too.
Some examples here in SO and other sources are constructed in the same way, so I'm wondering that nobody else has got the same problem. Seems that I'm missing anything. But what? I can't figure out, checked the docs multiple times.
Working Example:
from PyQt5.QtGui import *
from PyQt5.QtWidgets import *
from PyQt5.QtCore import *
import sys
class ECM(QWidget):
def __init__(self):
super(ECM, self).__init__()
self.setWindowTitle("Extended Context Menu")
self.lineEdit = QLineEdit()
self.lineEdit.setContextMenuPolicy(Qt.CustomContextMenu)
self.lineEdit.customContextMenuRequested.connect(self.my_contextMenuEvent)
layout = QVBoxLayout()
layout.addWidget(self.lineEdit)
self.setLayout(layout)
self.setFixedSize(800,200)
self.show()
def replace(self):
print("replace")
def my_contextMenuEvent(self):
print("my_contextMenuEvent")
menu = self.lineEdit.createStandardContextMenu()
action = QAction('&Replace', self)
action.setStatusTip('Replace values')
action.setShortcut(QKeySequence(Qt.CTRL + Qt.Key_R))
action.triggered.connect(self.replace)
menu.addAction(action)
menu.exec_()
if __name__ == '__main__':
app = QApplication(sys.argv)
sender = ECM()
app.exec_()

Based on musicamante's comment I came to the following solution:
Extract from the docs:
If you want to extend the standard context menu, reimplement this
function, call createStandardContextMenu() and extend the menu
returned.
The default use of the QAction list (as returned by actions()) is to
create a context QMenu.
It's not totally logically to me, not for the 1st time ;-)
Final code:
from PyQt5.QtGui import *
from PyQt5.QtWidgets import *
from PyQt5.QtCore import *
import sys
class ECM(QWidget):
def __init__(self):
super(ECM, self).__init__()
self.setWindowTitle("Extended Context Menu")
self.lineEdit = QLineEdit()
self.lineEdit.setContextMenuPolicy(Qt.CustomContextMenu)
self.lineEdit.customContextMenuRequested.connect(self.my_contextMenuEvent)
layout = QVBoxLayout()
layout.addWidget(self.lineEdit)
self.setLayout(layout)
self.setFixedSize(800,200)
action = QAction('&Replace', self)
action.setStatusTip('Replace values')
action.setShortcut(QKeySequence(Qt.CTRL + Qt.Key_R))
action.triggered.connect(self.replace)
self.lineEdit.addAction(action)
self.show()
def replace(self):
print("replace")
def my_contextMenuEvent(self):
menu = self.lineEdit.createStandardContextMenu()
menu.addActions(self.lineEdit.actions())
menu.exec_()
if __name__ == '__main__':
app = QApplication(sys.argv)
sender = ECM()
app.exec_()

Update PyQt menu

I am trying to dynamically update a menu with new items when I add new items via the form into Qsettings. For example, if you open my code and click the button and then click "new" it will open a QLineEdit with a button. When the button is clicked the list data gets stored via Qsettings.
I'd like to be able to update the menu somehow to show the items without restarting. I tried some things like calling repaint and update in a few areas with no luck.
Here is my code, I slimmed it down the best that I could for the example.
import functools
import sys
from PyQt5 import QtCore
from PyQt5.QtGui import QIcon
from PyQt5.QtWidgets import QWidget, QPushButton, QHBoxLayout, \
QVBoxLayout, QLineEdit,QApplication, QWidgetAction, QTextBrowser, QAction, QMenu
class MainWindow(QWidget):
def __init__(self, parent=None):
super(MainWindow, self).__init__(parent)
self.layout = QHBoxLayout()
self.menu_action = QAction(QIcon("icon.png"),"New", self)
self.menu_btn = QPushButton()
self.menu = MyMenu("Menu", self.menu_btn)
self.add_menu = self.menu.addMenu(QIcon("icon.png"), "Menu")
self.add_menu.addAction(self.menu_action)
self.menu_btn.setMenu(self.menu)
self.textBox = QTextBrowser(self)
action = QWidgetAction(self.menu_btn)
action.setDefaultWidget(self.textBox)
self.menu_btn.menu().addAction(action)
settings = QtCore.QSettings('test_org', 'my_app')
self.new_items = settings.value('new_item', [])
print('%s' % self.new_items)
for item in self.new_items:
self.create_action = QAction(QIcon("icon.png"), item[0], self)
self.create_action.setData(item)
self.add_menu.addAction(self.create_action)
self.create_action.triggered.connect(functools.partial(self.menu_clicked, self.create_action))
self.layout.addWidget(self.menu_btn)
self.setLayout(self.layout)
self.menu_action.triggered.connect(self.open_window)
def open_window(self):
self.create_menu_item = Create_Menu_Item()
self.create_menu_item.show()
def menu_clicked(self, item):
itmData = item.data()
print(itmData)
class Create_Menu_Item(QWidget):
def __init__(self, parent=None):
super(Create_Menu_Item, self).__init__(parent)
self.resize(200, 195)
self.layout = QVBoxLayout()
self.form = QLineEdit()
self.btn = QPushButton()
self.layout.addWidget(self.form)
self.layout.addWidget(self.btn)
self.btn.clicked.connect(self.save_new_item)
self.setLayout(self.layout)
def save_new_item(self):
settings = QtCore.QSettings('test_org', 'my_app')
self.new_item = settings.value('new_item', [])
self.new_item.append([self.form.text()])
settings.setValue('new_item', self.new_item)
print(self.new_item)
print('saved!')
class MyMenu(QMenu):
def event(self,event):
if event.type() == QtCore.QEvent.Show:
self.move(self.parent().mapToGlobal(QtCore.QPoint(0,0))-QtCore.QPoint(0,self.height()))
return super(MyMenu,self).event(event)
if __name__ == '__main__':
app = QApplication(sys.argv)
w = MainWindow()
w.show()
app.exec_()
Anyone have any ideas? Thanks.

You can create a for loop to access the list.
Bare in mind it is a list of lists so a nested for loop is neccessary
def save_new_item(self):
settings = QtCore.QSettings('test_org', 'my_app')
self.new_item = settings.value('new_item', [])
self.new_item.append([self.form.text()])
settings.setValue('new_item', self.new_item)
print(self.new_item)
print('saved!')
# Add new menu items..
for x in self.new_item:
for y in x:
print(y)
The above will keep adding the WHOLE list of items every time you add a new item..
To just add the newest item, this is all you need (the last item added to the list)
w.add_menu.addAction(self.new_item[0][-1])
so
def save_new_item(self):
settings = QtCore.QSettings('test_org', 'my_app')
self.new_item = settings.value('new_item', [])
self.new_item.append([self.form.text()])
settings.setValue('new_item', self.new_item)
print(self.new_item)
print('saved!')
#ADD last item in the list
w.add_menu.addAction(self.new_item[0][-1])

How to add widgets dynamically upon selecting an option from QComboBox in Pyqt5

I want to add widgets in GUI when a user selects a particular item from QComboBox.
With the different options in combo-box Pip config, I want GUI to look like as in the following images. In the right image, there are extra widgets present for an item Multi pip. Also I want the location of the extra widgets as shown in the right image.
How to add these widgets dynamically ? Please find the code below.
import sys
from PyQt5.QtWidgets import *
from PyQt5.QtGui import *
from PyQt5.QtCore import Qt, QRect
class Example(QWidget):
def __init__(self):
super(Example, self).__init__()
self.initUI()
def initUI(self):
vbox = QVBoxLayout()
CpsLabel = QLabel()
CpsLabel.setText("<font size = 12>Cps</font>")
CpsLabel.setAlignment(Qt.AlignCenter)
CpsLabel.setTextFormat(Qt.RichText)
CpsPipConfigLabel = QLabel('Pip config: ')
CpsPipConfigComboBox = QComboBox()
CpsPipConfigComboBox.addItems(['Single pip', 'Dual pip', 'Multi pip'])
CpsPipConfigComboBox.setCurrentIndex(2)
CpsChannel = QLabel('Cps channel: ')
CpsChannelComboBox = QComboBox()
CpsChannelComboBox.addItems(['A', 'B', 'C', 'D'])
CpsChannelComboBox.setCurrentIndex(0)
CpsTotalTeethLabel = QLabel('Total teeth: ')
CpsTotalTeethEdit = QLineEdit()
CpsTotalTeethEdit.setFixedWidth(50)
CpsTotalTeethEdit.setPlaceholderText('18')
CpsTotalTeethEdit.setValidator(QIntValidator())
CpsMissingTeethLabel = QLabel('Missing teeth: ')
CpsMissingTeethEdit = QLineEdit()
CpsMissingTeethEdit.setFixedWidth(50)
CpsMissingTeethEdit.setPlaceholderText('1')
CpsMissingTeethEdit.setValidator(QIntValidator())
vbox.addWidget(CpsLabel)
vbox.addStretch()
CpsQHBox1 = QHBoxLayout()
CpsQHBox1.setSpacing(0)
CpsQHBox1.addStretch()
CpsQHBox1.addWidget(CpsPipConfigLabel)
CpsQHBox1.addWidget(CpsPipConfigComboBox)
CpsQHBox1.addStretch()
vbox.addLayout(CpsQHBox1)
vbox.addStretch()
CpsQHBox2 = QHBoxLayout()
CpsQHBox2.setSpacing(0)
CpsQHBox2.addStretch()
CpsQHBox2.addSpacing(20)
CpsQHBox2.addWidget(CpsTotalTeethLabel)
CpsQHBox2.addWidget(CpsTotalTeethEdit)
CpsQHBox2.addStretch()
CpsQHBox2.addWidget(CpsMissingTeethLabel)
CpsQHBox2.addWidget(CpsMissingTeethEdit)
CpsQHBox2.addStretch()
vbox.addLayout(CpsQHBox2)
vbox.addStretch()
CpsQHBox3 = QHBoxLayout()
CpsQHBox3.setSpacing(0)
CpsQHBox3.addStretch()
CpsQHBox3.addWidget(CpsChannel)
CpsQHBox3.addWidget(CpsChannelComboBox)
CpsQHBox3.addStretch()
vbox.addLayout(CpsQHBox3)
vbox.addStretch()
self.setLayout(vbox)
self.setGeometry(200, 100, 300, 300)
self.setWindowTitle('Steady state data processing')
self.setWindowIcon(QIcon('duty_vs_suction_map_sum.png'))
self.setAutoFillBackground(True)
p = self.palette()
p.setColor(self.backgroundRole(), QColor(255,250,100))
# p.setColor(self.backgroundRole(), Qt.blue)
self.setPalette(p)
self.show()
if __name__ == '__main__':
app = QApplication(sys.argv)
ex = Example()
sys.exit(app.exec_())

I suggest you set the widgets up and place them at the beginning like you have them, but set them invisible. Then make a method that sets the appropriate widgets visible based on the qcombobox's current text and connect it to the qcombobox's activated signal.
You will also need to add self in front of almost every object so that it can be referred to from other methods.
class Example(QWidget):
def __init__(self):
super(Example, self).__init__()
self.initUI()
def initUI(self):
# setup code here...
self.CpsTotalTeethEdit.setVisible(False)
self.CpsTotalTeethLabel.setVisible(False)
self.CpsPipConfigComboBox.activated.connect(self.setup_total_teeth)
self.show()
def setup_widgets(self):
if self.CpsPipConfigComboBox.currentText() == "Multi pip":
self.CpsTotalTeethLabel.setVisible(True)
self.CpsTotalTeethEdit.setVisible(True)
By setting the items invisible instead of adding them with this method, you can also set them to be not visible when the cobobox's position is not for them.