Input Validation in QT

This post shows a form control widget that performs validation on its input. The invalid input is highlighted in red and the error message is display below the input. The input is validated in real-time (as the text is changed) when invalid the submit button is disabled and when valid it is enabled. The desired effect is shown below:

Code

	import sys
	from PyQt5.QtCore import pyqtSignal, QRegularExpression
	from PyQt5.QtWidgets import (QApplication, QFrame, QLabel, QLineEdit,
	QHBoxLayout, QVBoxLayout, QWidget, QPushButton)
	class FormGroup(QWidget):
	groupValidation = pyqtSignal(bool)
	def __init__(self, orientation='vertical'):
	super().__init__()
	self.form_controls = []
	self.main_layout = QVBoxLayout() if orientation == 'vertical' else QHBoxLayout()
	self.setLayout(self.main_layout)
	def addControl(self, control):
	if not isinstance(self, FormControl):
	self.form_controls.append(control)
	self.main_layout.addWidget(control)
	control.inputValidation.connect(self.validateGroup)
	else:
	raise ValueError('could not add object of type {}'.format(type(control)))
	def validateGroup(self, _):
	for control in self.form_controls:
	if not control.valid:
	self.groupValidation.emit(False)
	return
	self.groupValidation.emit(True)
	class FormControl(QWidget):
	inputValidation = pyqtSignal(bool)
	def __init__(self, title=''):
	super().__init__()
	control_layout = QVBoxLayout()
	self.form_label = QLabel()
	self.form_control = QLineEdit()
	self.validation_label = QLabel()
	self.validation_label.setStyleSheet('color: red')
	control_layout.addWidget(self.form_label)
	control_layout.addWidget(self.form_control)
	control_layout.addWidget(self.validation_label)
	control_layout.addStretch(1)
	self.setLayout(control_layout)
	self.title = title
	self.required = False
	self.required_error_message = '{} is required.'
	self.email = False
	self.email_error_message = 'The value should be an email.'
	self.email_regex = QRegularExpression("\\b[A-Z0-9._%+-]+@[A-Z0-9.-]+\\.[A-Z]{2,4}\\b",
	QRegularExpression.CaseInsensitiveOption)
	self.number = False
	self.number_error_message = '{} should be a number.'
	self._minimum = None
	self.min_error_message = '{} should be higher than {}.'
	self._maximum = None
	self.max_error_message = '{} should be lower than {}.'
	self.valid = False
	self.form_control.textChanged.connect(self.validate)
	@property
	def title(self):
	return self._title
	@title.setter
	def title(self, title):
	self._title = title
	self.form_label.setText('{}:'.format(self._title))
	@property
	def maximum(self):
	return self._maximum
	@maximum.setter
	def maximum(self, value):
	self._maximum = value
	self.number = True
	@property
	def minimum(self):
	return self._minimum
	@minimum.setter
	def minimum(self, value):
	self._minimum = value
	self.number = True
	def range(self, minimum, maximum):
	self._minimum = minimum
	self._maximum = maximum
	self.number = True
	def validate(self, input_text):
	text = input_text.strip()
	if self.required and not text:
	self.onInvalid(self.required_error_message.format(self.title))
	return
	if self.email and not self.email_regex.match(text).hasMatch():
	self.onInvalid(self.email_error_message)
	return
	if self.number:
	value, ok = self.isNumber(text)
	if not ok:
	self.onInvalid(self.number_error_message.format(self.title))
	return
	if self._maximum is not None and value > self._maximum:
	self.onInvalid(self.max_error_message.format(self.title, self._maximum))
	return
	if self._minimum is not None and value < self._minimum:
	self.onInvalid(self.min_error_message.format(self.title, self._minimum))
	return
	self.onValid()
	def onValid(self):
	self.form_control.setStyleSheet('')
	self.validation_label.setText('')
	self.valid = True
	self.inputValidation.emit(True)
	def onInvalid(self, error_message):
	self.form_control.setStyleSheet('border: 1px solid red;')
	self.validation_label.setText(error_message)
	self.valid = False
	self.inputValidation.emit(False)
	def isNumber(self, value):
	try:
	return float(value), True
	except ValueError:
	return None, False
	class Window(QWidget):
	def __init__(self):
	super().__init__()
	self.setWindowTitle('Validation Demo')
	self.setMinimumSize(400, 300)
	layout = QVBoxLayout()
	name = FormControl('Name')
	name.required = True
	email = FormControl('Email')
	email.required = True
	email.email = True
	age = FormControl('Age')
	age.required = True
	age.range(18, 80)
	self.button = QPushButton('Submit')
	self.button.setDisabled(True)
	self.group = FormGroup()
	self.group.groupValidation.connect(self.formValidation)
	self.group.addControl(name)
	self.group.addControl(email)
	self.group.addControl(age)
	button_layout = QHBoxLayout()
	button_layout.addStretch(1)
	button_layout.addWidget(self.button)
	layout.addWidget(self.group)
	layout.addLayout(button_layout)
	layout.addStretch(1)
	self.setLayout(layout)
	def formValidation(self, is_valid):
	if is_valid:
	self.button.setEnabled(True)
	else:
	self.button.setDisabled(True)
	if __name__ == '__main__':
	app = QApplication(sys.argv)
	w = Window()
	w.show()
	sys.exit(app.exec_())

view raw validation.py hosted with ❤ by GitHub