python - QLabel is not updated unless the mainWindow is unfocused

Question

I am trying "Hello World" using PyQt5 with Python 3.7.3 and macOS 10.14.6. Executing pyqt_helloworld.py below and clicking the button will update the label to "Hello World".

However, when the button is clicked, the text is not changed, and it is not until I focus on the window of other application manually that the label is updated. How can I update QLabel without unfocusing the PyQt application?

Thanks in advance!

pyqt_helloworld_ui.py

from PyQt5 import QtCore, QtGui, QtWidgets

class Ui_HelloWorld(object):
    def setupUi(self, Dialog):
        Dialog.setObjectName("Dialog")
        Dialog.resize(400, 300)
        self.label = QtWidgets.QLabel(Dialog)
        self.label.setGeometry(QtCore.QRect(70, 40, 201, 21))
        self.label.setObjectName("label")
        self.pushButton = QtWidgets.QPushButton(Dialog)
        self.pushButton.setGeometry(QtCore.QRect(130, 90, 113, 32))
        self.pushButton.setObjectName("pushButton")

        self.retranslateUi(Dialog)
        QtCore.QMetaObject.connectSlotsByName(Dialog)

    def retranslateUi(self, Dialog):
        _translate = QtCore.QCoreApplication.translate
        Dialog.setWindowTitle(_translate("Dialog", "Dialog"))
        self.label.setText(_translate("Dialog", "foobar"))
        self.pushButton.setText(_translate("Dialog", "Click"))

pyqt_helloworld.py

import sys

from PyQt5.QtCore import pyqtSlot
from PyQt5.QtWidgets import QApplication
from PyQt5.QtWidgets import QMainWindow

from pyqt_helloworld_ui import Ui_HelloWorld


class HelloWorldGui(QMainWindow, Ui_HelloWorld):
    def __init__(self, parent=None):
        super(HelloWorldGui, self).__init__(parent)
        self.setupUi(self)
        self.pushButton.clicked.connect(self.setTextHelloWorld)

    def setTextHelloWorld(self):
        self.label.setText("Hello World")


if __name__ == '__main__':
    argvs = sys.argv
    app = QApplication(argvs)
    hello_world_gui = HelloWorldGui()
    hello_world_gui.show()
    sys.exit(app.exec_())

It works correctly even though there is an error: change QMainWindow to QDialog. Are you using the latest version of PyQt5? What is your OS? What is your version of Python? How have you installed PyQt5? — eyllanesc
Thank you for your comment. - I installed PyQt5 by pip install PyQt5 and it's version is 5.13.0 (latest) - I'm using macOS 10.14.6. - Changing QMainWindow to QDialog in pyqt_helloworld.py does not work. — I-was-a-Ki
I think it's a bug, in Linux with Python 3.7.4 and PyQt5 5.13 it works correctly, report it. — eyllanesc
Sorry for my late reply. I tried the code above in macOS Sierra and confirmed it works correctly, so it might be a problem caused by the recent update in macOS. Thank you very much for your help! — I-was-a-Ki

Olivier Friard Olivier Friard · Accepted Answer · 2019-08-20T10:41:41

the issue is present in PyQt5 since 5.11.0 (tested 5.11.x, 5.12.x and 5.13) and PySide2 v.5.13 on MacOS (tested 10.14 and 10.12.6). The v.5.10.1 works fine. The issue does not exist under Linux and Windows Adding a call to the repaint method fix the issue.

def setTextHelloWorld(self):
    self.label.setText("Hello World")
    self.label.repaint()

python - QLabel is not updated unless the mainWindow is unfocused

1 Answers