Appending multiple Python 3 QStandardItems on 1 QStandardItem row - pyqt5

Question

I'd like to concatenate more than 1 QStandardItem to 1 row of a QTreeView and have all QStandardItems be displayed. At present only the first item in the QList being sent to appendRow() is being displayed. I've searched the pyqt5 documentation but haven't found an explanation for displaying multiple QStandardItems once appended to a row. I'm using Python 3.8. Here is my code:
from PyQt5.QtWidgets import QApplication, QMainWindow
from PyQt5.Qt import QStandardItemModel, QStandardItem
from PyQt5.QtGui import QFont, QColor
from PyQt5.QtWidgets import QWidget, QTabWidget, QTreeView
from PyQt5 import QtCore
import sys
DefaultFont = "Droid Sans"
DefaultFontColor = "black"
DefaultBackgroundColor = "white"
class StandardItem(QStandardItem):
def __init__(self, txt='', font=DefaultFont, fontSize=10, setBold=False, fgColor=DefaultFontColor, bgColor=DefaultBackgroundColor):
super().__init__()
defFont = QFont(font, fontSize)
defFont.setBold(setBold)
self.setEditable(False)
self.setBackground(QColor(bgColor))
self.setForeground(QColor(fgColor))
self.setFont(defFont)
self.setText(txt)
#end __init__
#end class StandardItem
class MyMainWindow(object):
def __init__(self, MainWindow):
self.__addToTree(MainWindow)
#end __init__()
def __addToTree(self, MainWindow):
MainWindow.resize(640, 500)
self.centralWidget = QWidget(MainWindow)
self.centralWidget.setObjectName("centralWidget")
self.tabWidget = QTabWidget(self.centralWidget)
self.tabWidget.setGeometry(QtCore.QRect(10, 50, 620, 440))
self.tabWidget.setObjectName("tabWidget")
MainWindow.setCentralWidget(self.centralWidget)
self.myTab= QWidget()
self.treeView = QTreeView(self.myTab)
self.treeModel = QStandardItemModel()
self.treeRootNode = self.treeModel.invisibleRootItem()
self.treeView.setGeometry(QtCore.QRect(7, 7, 900, 600))
self.tabWidget.addTab(self.myTab, "")
item1row1 = StandardItem("Row 1: Hi There!", fontSize=10, setBold=False)
item1row2 = StandardItem("This is row 2, item1", fontSize=11, setBold=True, fgColor="blue", bgColor="antiquewhite")
item2row2 = StandardItem("This is row 2, item2", fontSize=12, setBold=True, fgColor="yellowgreen")
item3row2 = StandardItem("This is row 2, item3", fontSize=12, setBold=True, fgColor="red")
item1row1.appendRow((item1row2, item2row2, item3row2))
self.treeRootNode.appendRow(item1row1)
self.treeView.setModel(self.treeModel)
#end __addToTree()
#end class MyMainWindow
qtApp = QApplication(sys.argv)
MainWindow = QMainWindow()
myMainWindow = MyMainWindow(MainWindow)
MainWindow.show()
sys.exit(qtApp.exec_())

Answer 1

The column count of a tree view is always based on the column count of the root index, which is the index that contains all top level items (invisibleRootItem() for QStandardItemModel).
For QStandardItemModel, unless explicitly set using setColumnCount(), the column count is always the maximum column count of all top level rows. In your case, you only have a top level row with just one item, so the view thinks that there is only one column, and all the remaining items of the top level items will not be visible.
So, you have 2 possibilities:
manually set the column count, either by using setColumnCount(3) or by adding the row/column arguments in the constructor (QStandardItemModel(0, 3));
use appendRow() with None as placeholders for the remaining columns: treeRootNode.appendRow((item1row1, None, None));
Note: you're not expected to modify a pyuic file, as it's considered bad practice for a lot of reasons; follow the official guidelines about using Designer instead. You should also always use layout managers.