customWidget.py

class MainWidget(QtWidgets.QMainWindow):
    def __init__(self, parent=None):
        self.connectSignal()
    
    def connectSignal(self):
        self.someBtn.clicked.connect(self.openCustomWidget)
    
    def openCustomWidget(self):
        # initialize with a widget and a layout
        self.customWidget = QtWidgets.QWidget()
        layout = QtWidgets.QHBoxLayout(self.customWidget)
        
        # title
        self.customWidget.setWindowTitle('Error Log')
        
        # set window display behavior
        self.customWidget.setWindowFlags(QtCore.Qt.WindowStaysOnTopHint)
        
        # set window icon (using a built-in icon)
        name = "SP_MessageBoxCritical"
        style = self.customWidget.style()
        icon = style.standardIcon(getattr(QtWidgets.QStyle, name))
        self.customWidget.setWindowIcon(icon)
        
        # add custom elements here
        message = "happy new year"
        errorLabel = QtWidgets.QLabel(messages)
        scrollArea = QtWidgets.QScrollArea()
        scrollArea.setWidgetResizable(True)
        scrollArea.setWidget(errorLabel)
        
        # finalize
        layout.addWidget(scrollArea)
        self.customWidget.show()

def showWindow():
    win = MainWidget()
    try:
        win.close()
    except:
        pass
    win.setAttribute(QtCore.Qt.WA_DeleteOnClose)
    win.show()