How to access attribut from one class to another class in PyQt5 / PySide2

Question

I cannot get access to attribut self.horizontalLayout_Base in class Ui_MainWindow where I want add new widgets.

There is:

1. Main class MainWindow which inherits class Ui_MainWindow .
2. Class Ui_MainWindow creates layout.
3. Class Dialog provides additional information and confirmation or cancellation.

Main class MainWindow calls class Dialog . Class Dialog is queried and then the method tableWidget in class MainWindow is called. But there is not access to attribut self.horizontalLayout_Base which was creating by class Ui_MainWindow .

Is there any way to get access?

Main class MainWindow

class MainWindow(QtWidgets.QMainWindow, Ui_MainWindow):
    
    def __init__(self, *args, obj=None, **kwargs):
        super(MainWindow, self).__init__(*args, **kwargs)
        
        ...
        
        self.setupUi(self)
        
        ...
        
        
    def tableWidget(self):
        if len(list) > 0:
            row = len(list)
            clmn = len(list[0]) 
            self.tableWidget = QTableWidget(row, clmn + 1)
        else:
            return
        self.vbox = QVBoxLayout()

        ...

        Ui_MainWindow.gridLayout_Base.addLayout(self.vbox) # Here I want to get access

Layout class Ui_MainWindow

class Ui_MainWindow(object):

    def setupUi(self, MainWindow):
        MainWindow.setObjectName("MainWindow")
        MainWindow.resize(1110, 772)
        sizePolicy = QtWidgets.QSizePolicy(QtWidgets.QSizePolicy.Expanding, QtWidgets.QSizePolicy.Expanding)
        sizePolicy.setHorizontalStretch(0)
        sizePolicy.setVerticalStretch(0)
        sizePolicy.setHeightForWidth(MainWindow.sizePolicy().hasHeightForWidth())
        MainWindow.setSizePolicy(sizePolicy)
        self.centralwidget = QtWidgets.QWidget(MainWindow)
        sizePolicy = QtWidgets.QSizePolicy(QtWidgets.QSizePolicy.Expanding, QtWidgets.QSizePolicy.Expanding)
        sizePolicy.setHorizontalStretch(0)
        sizePolicy.setVerticalStretch(0)
        sizePolicy.setHeightForWidth(self.centralwidget.sizePolicy().hasHeightForWidth())
        self.centralwidget.setSizePolicy(sizePolicy)
        self.centralwidget.setObjectName("centralwidget")
        self.gridLayout = QtWidgets.QGridLayout(self.centralwidget)
        self.gridLayout.setObjectName("gridLayout")

        self.horizontalLayout_Base = QtWidgets.QHBoxLayout() # This is target

        ...

Class Dialog

class Dialog(QDialog):

    NumGridRows = 3
    NumButtons = 4

    def __init__(self, souradnice):
        super(Dialog, self).__init__()
        ...

    def buttonAccepted(self):
        ...

        MainWindow.tableWidget(self)
        self.close()

Answer 1

It seems like you're confusing what classes, instances and their methods are (for this, I strongly suggest you to do some research, as they are fundamental aspects of OOP and cannot be ignored).

In tableWidget you cannot access gridLayout_Base from Ui_MainWindow , because that's a class. Since you're both inheriting from QMainWindow and Ui_MainWindow, and you're calling setupUi(self) that means that all attributes of the ui are actually created as attribute members of the instance , so you can access the layout just by using self.gridLayout_Base .
Then, if you're adding a layout, you must use addLayout() , not addWidget() (which is for widgets only).

    def tableWidget(self):
        # ...
        self.gridLayout_Base.(self.vbox)

Then, I don't know how you're creating and opening the dialog, but you certainly cannot call MainWindow.tableWidget(self) : that would result in calling that method with the dialog instance as first argument (self), so you won't be adding anything to the main window.

A better and safer way (which is also the commonly accepted practice) is to show the dialog as modal by calling its exec() , and then react to it according to the result. In order to correcty achieve this, you should not call self.close() on the dialog (which results in rejecting it) but self.accept() .

class MainWindow(QtWidgets.QMainWindow, Ui_MainWindow):
    # ...
    def someFunctionToShowDialog(self):
        dialog = Dialog(self)
        if :
            parameters = dialog.getValues()
            self.tableWidget()
            self.doSomethingWithParameters(parameters)


class Dialog(QDialog):
    # ...
    def buttonAccepted(self):
        

    def getValues(self):
        return self.someValue, self.anotherValue