PyQt5 update MainWindow after paintEvent

Question

I am pretty new to QT. I am trying to paint some rectangles after button click. paintEvent method seems to working but after button click nothing happens I think I need to update mainWindow somehow. Code:

from PyQt5 import QtCore, QtGui, uic, QtWidgets
from PyQt5.QtWidgets import QMainWindow, QApplication
from PyQt5.QtGui import QPainter, QColor, QBrush

qtCreatorFile = "gui.ui" # Enter file here.

#This is where you add the file you created earlier. It is loaded using the inbuilt function
Ui_MainWindow, QtBaseClass = uic.loadUiType(qtCreatorFile)

class MyApp(QtWidgets.QMainWindow):

    pridat_slide = False

    def __init__(self):
        super(MyApp, self).__init__()
        self.ui = Ui_MainWindow()
        self.ui.setupUi(self)
        self.ui.pridaj_slide.clicked.connect(self.pridaj_slide)


    def pridaj_slide(self):
        self.pridat_slide = True

    def paintEvent(self, e):
        qp = QPainter()
        qp.begin(self)
        self.drawRectangles(qp)
        qp.end()

    def drawRectangles(self, qp):
        if self.pridat_slide:
            print ("test");

            qp.setBrush(QColor(200, 0, 0))
            qp.drawRect(10, 15, 90, 60)

            qp.setBrush(QColor(255, 80, 0, 160))
            qp.drawRect(130, 15, 90, 60)

            qp.setBrush(QColor(25, 0, 90, 200))
            qp.drawRect(250, 15, 90, 60)
            self.update()
            self.pridat_slide = False

if __name__ == "__main__":
    try:
        app = QtWidgets.QApplication(sys.argv)
        window = MyApp()
        window.show()
        sys.exit(app.exec_())

screen: "test" is printed

Thanks for any suggestions & improvements.

SOLVED

Problem was in background-color of MainWindow. I deleted background-color: rgb(145,145,145); and rectangles are up.

Answer 1

you can call self.repaint() to update the display (it will call paintEvent again) in your pridaj_slide function :

def pridaj_slide(self):
    self.pridat_slide = True
    self.repaint()