PyQt5 button to run function and update LCD

Question

I am getting started with creating GUI\'s in PyQt5 with Python 3. At the click of the button I want to run the \"randomint\" function and display the returned integer to th

Answer 1

The problem is that the button.clicked.connect expects the slot (Python callable object), but lcd.display returns None. So we need a simple function (slot) for button.clicked.connect which will display your newly generated value. This is working version:

import sys
from PyQt5.QtWidgets import QApplication, QWidget, QVBoxLayout, QPushButton, QLCDNumber
from random import randint


class Window(QWidget):
    def __init__(self):
        super().__init__()
        self.initui()


    def initui(self):
        self.lcd = QLCDNumber(self)

        button = QPushButton('Generate', self)
        button.resize(button.sizeHint())

        layout = QVBoxLayout()
        layout.addWidget(self.lcd)
        layout.addWidget(button)

        self.setLayout(layout)
        button.clicked.connect(self.handleButton)

        self.setGeometry(300, 500, 250, 150)
        self.setWindowTitle('Rand Integer')
        self.show()


    def handleButton(self):
        self.lcd.display(self.randomint())


    def randomint(self):
        random = randint(2, 99)
        return random


if __name__ == '__main__':

    app = QApplication(sys.argv)
    ex = Window()
    sys.exit(app.exec_())

Answer 2

Another way of resolving the TypeError: argument 1 has unexpected type 'NoneType is to prefix your slot with lambda: like so:

self.tableWidget.cellChanged['int','int'].connect(lambda:self.somefunction())

I actually don't know why but it's a solution that worked for me.