PYQT5: Is it possible in python to send back a value from a QDialog without closing it?

Question

Is it possible for a QDialog to send a value back to the application without also closing the dialog window? A common example would be the insert symbol dialog in Microsoft Word. (In fact, this is what I am trying to replicate.)

I have included some basic code for a main window with a label and a button. Pushing the button opens the dialog window. The dialog window contains a textLineEdit widget, an OK button, and a Cancel button. After pushing OK any text entered into the dialog's textLineEdit is set as the text in the main window's label. Would it be possible to return the entered text without closing the dialog? I know it would require some on_OK_clicked procedure in the Dialog class, but I cannot seem to return a value without also closing the dialog. Any ideas would be greatly appreciated.

import sys
from PyQt5 import QtCore, QtWidgets

class Ui_MainWindow(object):
    def setupUi(self, MainWindow):
        MainWindow.setObjectName("MainWindow")
        MainWindow.resize(320, 86)
        self.centralwidget = QtWidgets.QWidget(MainWindow)
        self.centralwidget.setObjectName("centralwidget")
        self.verticalLayout = QtWidgets.QVBoxLayout(self.centralwidget)
        self.verticalLayout.setObjectName("verticalLayout")
        self.label = QtWidgets.QLabel(self.centralwidget)
        self.label.setObjectName("label")
        self.verticalLayout.addWidget(self.label)
        spacerItem = QtWidgets.QSpacerItem(20, 13, QtWidgets.QSizePolicy.Minimum, QtWidgets.QSizePolicy.Expanding)
        self.verticalLayout.addItem(spacerItem)
        self.pushButton = QtWidgets.QPushButton(self.centralwidget)
        self.pushButton.setObjectName("pushButton")
        self.verticalLayout.addWidget(self.pushButton)
        MainWindow.setCentralWidget(self.centralwidget)

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

    def retranslateUi(self, MainWindow):
        _translate = QtCore.QCoreApplication.translate
        MainWindow.setWindowTitle(_translate("MainWindow", "MainWindow"))
        self.label.setText(_translate("MainWindow", "TextLabel"))
        self.pushButton.setText(_translate("MainWindow", "Open Dialog"))

class Ui_Dialog(object):
    def setupUi(self, Dialog):
        Dialog.setObjectName("Dialog")
        Dialog.resize(400, 94)
        self.lineEdit = QtWidgets.QLineEdit(Dialog)
        self.lineEdit.setGeometry(QtCore.QRect(20, 20, 361, 22))
        self.lineEdit.setObjectName("lineEdit")
        self.buttonBox = QtWidgets.QDialogButtonBox(Dialog)
        self.buttonBox.setGeometry(QtCore.QRect(40, 50, 341, 32))
        self.buttonBox.setOrientation(QtCore.Qt.Horizontal)
        self.buttonBox.setStandardButtons(QtWidgets.QDialogButtonBox.Cancel|QtWidgets.QDialogButtonBox.Ok)
        self.buttonBox.setObjectName("buttonBox")

        self.retranslateUi(Dialog)
        self.buttonBox.accepted.connect(Dialog.accept) # type: ignore
        self.buttonBox.rejected.connect(Dialog.reject) # type: ignore
        QtCore.QMetaObject.connectSlotsByName(Dialog)

    def retranslateUi(self, Dialog):
        _translate = QtCore.QCoreApplication.translate
        Dialog.setWindowTitle(_translate("Dialog", "Dialog"))

class Dialog(QtWidgets.QDialog, Ui_Dialog):
    def __init__(self, parent=None):
        QtWidgets.QDialog.__init__(self, parent)
        self.setupUi(self)

class MainWindow(QtWidgets.QMainWindow, Ui_MainWindow):
    def __init__(self, parent=None):
        QtWidgets.QMainWindow.__init__(self, parent)
        self.setupUi(self)
        self.pushButton.clicked.connect(self.onClicked)

    def onClicked(self):
        dlg = Dialog()
        if dlg.exec_():
            self.label.setText(dlg.lineEdit.text())

if __name__ == '__main__':
    app = QtWidgets.QApplication(sys.argv)
    w = MainWindow()
    w.show()
    sys.exit(app.exec_())

Answer 1

Thanks to ekhumoro for the help I needed. The solution was to use an Apply button in the QDialogButtonBox and to connect the click action to a slot in the main window. In this case, I found I had to use a lambda function as the slot. (This is the last piece I was missing.) dlg.buttonBox.button(QtWidgets.QDialogButtonBox.Apply).clicked.connect(lambda: self.label.setText(dlg.lineEdit.text()))

Here is the full working code.

import sys
from PyQt5 import QtCore, QtWidgets

class Ui_MainWindow(object):
    def setupUi(self, MainWindow):
        MainWindow.setObjectName("MainWindow")
        MainWindow.resize(320, 86)
        self.centralwidget = QtWidgets.QWidget(MainWindow)
        self.centralwidget.setObjectName("centralwidget")
        self.verticalLayout = QtWidgets.QVBoxLayout(self.centralwidget)
        self.verticalLayout.setObjectName("verticalLayout")
        self.label = QtWidgets.QLabel(self.centralwidget)
        self.label.setObjectName("label")
        self.verticalLayout.addWidget(self.label)
        spacerItem = QtWidgets.QSpacerItem(20, 13, QtWidgets.QSizePolicy.Minimum, QtWidgets.QSizePolicy.Expanding)
        self.verticalLayout.addItem(spacerItem)
        self.pushButton = QtWidgets.QPushButton(self.centralwidget)
        self.pushButton.setObjectName("pushButton")
        self.verticalLayout.addWidget(self.pushButton)
        MainWindow.setCentralWidget(self.centralwidget)

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

    def retranslateUi(self, MainWindow):
        _translate = QtCore.QCoreApplication.translate
        MainWindow.setWindowTitle(_translate("MainWindow", "MainWindow"))
        self.label.setText(_translate("MainWindow", "TextLabel"))
        self.pushButton.setText(_translate("MainWindow", "Open Dialog"))

class Ui_Dialog(object):
    def setupUi(self, Dialog):
        Dialog.setObjectName("Dialog")
        Dialog.resize(400, 94)
        self.lineEdit = QtWidgets.QLineEdit(Dialog)
        self.lineEdit.setGeometry(QtCore.QRect(20, 20, 361, 22))
        self.lineEdit.setObjectName("lineEdit")
        self.buttonBox = QtWidgets.QDialogButtonBox(Dialog)
        self.buttonBox.setGeometry(QtCore.QRect(40, 50, 341, 32))
        self.buttonBox.setOrientation(QtCore.Qt.Horizontal)
        self.buttonBox.setStandardButtons(QtWidgets.QDialogButtonBox.Close|QtWidgets.QDialogButtonBox.Apply)
        self.buttonBox.button(QtWidgets.QDialogButtonBox.Apply).setText("Insert")
        self.buttonBox.setObjectName("buttonBox")

        self.retranslateUi(Dialog)
        self.buttonBox.rejected.connect(Dialog.reject) # type: ignore
        QtCore.QMetaObject.connectSlotsByName(Dialog)

    def retranslateUi(self, Dialog):
        _translate = QtCore.QCoreApplication.translate
        Dialog.setWindowTitle(_translate("Dialog", "Dialog"))

class Dialog(QtWidgets.QDialog, Ui_Dialog):

    def __init__(self, parent=None):
        QtWidgets.QDialog.__init__(self, parent)
        self.setupUi(self)

class MainWindow(QtWidgets.QMainWindow, Ui_MainWindow):
    def __init__(self, parent=None):
        QtWidgets.QMainWindow.__init__(self, parent)
        self.setupUi(self)
        self.pushButton.clicked.connect(self.onClicked)

    def onClicked(self):
        dlg = Dialog()
        dlg.buttonBox.button(QtWidgets.QDialogButtonBox.Apply).clicked.connect(lambda: self.label.setText(dlg.lineEdit.text()))
        dlg.exec()

if __name__ == '__main__':
    app = QtWidgets.QApplication(sys.argv)
    w = MainWindow()
    w.show()
    sys.exit(app.exec_())