**Course Title:** PySide6 Application Development **Section Title:** Advanced Widgets and Forms **Topic:** Customizing forms with QLabel and QLineEdit validators **Overview** In the previous topics, we covered various widgets and form elements, including QLabel and QLineEdit. In this topic, we will delve into customizing these widgets to create robust and user-friendly forms. We will explore how to use validators to restrict input data and provide feedback to users. **What are validators?** Validators are objects that check the input data against certain criteria. They are commonly used in forms to ensure that users enter valid data, such as email addresses, phone numbers, or passwords. Qt provides several built-in validators, including QIntValidator, QDoubleValidator, and QRegExpValidator. **Using QLabel and QLineEdit validators** To use validators with QLabel and QLineEdit, we need to create a validator object and then set it to the QLineEdit widget using the setValidator() method. Here's an example: ```python import sys from PySide6.QtWidgets import QApplication, QWidget, QLineEdit, QLabel, QVBoxLayout from PySide6.QtGui import QIntValidator, QRegExpValidator class ValidatorForm(QWidget): def __init__(self): super().__init__() self.initUI() def initUI(self): layout = QVBoxLayout() # Create a QLabel and QLineEdit for integer input label1 = QLabel("Enter an integer between 1 and 10:") intEdit = QLineEdit() intValidator = QIntValidator(1, 10, intEdit) intEdit.setValidator(intValidator) # Create a QLabel and QLineEdit for email input label2 = QLabel("Enter an email address:") emailEdit = QLineEdit() emailRegex = "^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$" emailValidator = QRegExpValidator(emailRegex) emailEdit.setValidator(emailValidator) layout.addWidget(label1) layout.addWidget(intEdit) layout.addWidget(label2) layout.addWidget(emailEdit) self.setLayout(layout) self.setWindowTitle("Validator Form") self.show() def main(): app = QApplication(sys.argv) ex = ValidatorForm() sys.exit(app.exec()) if __name__ == "__main__": main() ``` In this example, we create two QLabel and QLineEdit pairs, one for integer input and one for email input. We create a QIntValidator for the integer input and a QRegExpValidator for the email input. We then set the validators to the respective QLineEdit widgets using the setValidator() method. **Key concepts** * Validators are used to restrict input data and provide feedback to users. * Qt provides several built-in validators, including QIntValidator, QDoubleValidator, and QRegExpValidator. * Validators are set to QLineEdit widgets using the setValidator() method. **Practical takeaways** * Use validators to restrict input data and improve user experience. * Use the setValidator() method to set validators to QLineEdit widgets. * Use the QIntValidator, QDoubleValidator, and QRegExpValidator classes to create custom validators. **Resources** * [Qt Validator Documentation](https://doc.qt.io/qtforpython/PySide6/QtGui/QValidator.html) * [Qt Regex Validator Documentation](https://doc.qt.io/qtforpython/PySide6/QtGui/QRegExpValidator.html) **Next topic** In the next topic, we will cover "Creating reusable custom widgets". Do you have any questions or comments about this topic? Please leave a comment below.