How to Avoid Freezing Your PyQt GUI: Alternatives to time.sleep?

Freezing GUI: Alternatives to time.sleep in PyQt Applications

PyQt applications often encounter issues when using time.sleep due to its freezing effect on the GUI thread. To address this, alternative solutions are necessary.

Utilizing QTimer for Delayed Actions

One option is to utilize QTimer. However, this method requires linking the timer to a separate function, which may not be suitable for situations where you want to continue with the current function after a delay.

QTest.qWait: A Non-Blocking Sleep Function

An alternative solution is to employ QTest.qWait from the PyQt4 module. This function simulates the behavior of time.sleep without blocking the GUI thread. The syntax is as follows:

from PyQt4 import QtTest

QtTest.QTest.qWait(msecs)

Where "msecs" represents the desired delay in milliseconds. Unlike time.sleep, QTest.qWait allows the GUI to remain responsive during the delay.

Example Usage

To illustrate the usage of QTest.qWait, consider the following code snippet:

import sys
from PyQt5.QtWidgets import QMainWindow, QLabel, QWidget, QVBoxLayout

class Example(QMainWindow):
    def __init__(self):
        super().__init__()

        self.initUI()

    def initUI(self):
        self.label = QLabel("Waiting...")
        self.setCentralWidget(self.label)

        QtTest.QTest.qWait(2000)

        self.label.setText("Finished waiting")

if __name__ == '__main__':
    app = QApplication(sys.argv)
    ex = Example()
    ex.show()
    sys.exit(app.exec_())

In this example, the GUI remains responsive while the application waits for 2 seconds using QTest.qWait. After the delay, the text of the label is updated.

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