User Input Validation in PyQt5 and Python

Question

This is a two part question about input validation with one specific and another more general component.

The specific:

While researching the

Answer 1

You can set different validators for different QLineEdit objects.

QRegExpValidator has two constructors:

QRegExpValidator(parent: QObject = None)
QRegExpValidator(QRegExp, parent: QObject = None)

so, you should change your code to:

reg_ex = QRegExp("[0-9]+.?[0-9]{,2}")
input_validator = QRegExpValidator(reg_ex, self.le_input)
self.le_input.setValidator(input_validator)

Once you set validator for QLineEdit, there is no need to use

self.le_input.textChanged.connect(self.validate_input)

Just delete it. And that should work fine.

If you want to find documentation about PyQt5, you can simple use this in your console:

pydoc3 PyQt5.QtGui.QRegExpValidator

But pydoc can only show you little information, so you should use C++ version documation as well.

Finally, an example about this:

from PyQt5.Qt import QApplication
from PyQt5.QtCore import QRegExp
from PyQt5.QtGui import QRegExpValidator
from PyQt5.QtWidgets import QWidget, QLineEdit

import sys

class MyWidget(QWidget):
    def __init__(self, parent=None):
        super(QWidget, self).__init__(parent)
        self.le_input = QLineEdit(self)

        reg_ex = QRegExp("[0-9]+.?[0-9]{,2}")
        input_validator = QRegExpValidator(reg_ex, self.le_input)
        self.le_input.setValidator(input_validator)

if __name__ == '__main__':
    a = QApplication(sys.argv)

    w = MyWidget()
    w.show()

    a.exec()