How to fix enter press detection in PyQt5

Question

So I've made GUI for my chat using PyQt5. I connected one button with the function to handle sending message, but I want it to do the same when I press enter.

def send_message(self):
    message = self.plainTextEdit.toPlainText()
    if message.strip(' ') != '':
        self.textBrowser.append(message)
    self.plainTextEdit.clear()

def enter_handler(self, event):
    print(event.key())
    if event.key() == QtCore.Qt.Key_Enter:
        self.send_message()
    else:
        keyPressEvent(qKeyEvent)
    event.accept()

if __name__ == "__main__":
    import sys
    app = QtWidgets.QApplication(sys.argv)
    mainWindow = QtWidgets.QMainWindow()
    ui = Ui_mainWindow()
    ui.setupUi(mainWindow)
    mainWindow.show()
    sys.exit(app.exec_())

I've already tried to change QtCore.Qt.Key_Enter to QtCore.Qt.Key_Return, but it didn't work. Thanks in advance!

import sys
from PyQt5 import QtCore, QtGui, QtWidgets


class Ui_mainWindow(object):
    def setupUi(self, mainWindow):
        mainWindow.setObjectName("mainWindow")
        mainWindow.resize(406, 686)
        self.centralwidget = QtWidgets.QWidget(mainWindow)
        self.centralwidget.setObjectName("centralwidget")
        self.verticalLayout_2 = QtWidgets.QVBoxLayout(self.centralwidget)
        self.verticalLayout_2.setObjectName("verticalLayout_2")
        self.verticalLayout = QtWidgets.QVBoxLayout()
        self.verticalLayout.setObjectName("verticalLayout")
        self.textBrowser = QtWidgets.QTextBrowser(self.centralwidget)
        font = QtGui.QFont()
        font.setPointSize(13)
        font.setBold(False)
        font.setWeight(50)
        self.textBrowser.setFont(font)
        self.textBrowser.setObjectName("textBrowser")
        self.verticalLayout.addWidget(self.textBrowser)
        self.plainTextEdit = QtWidgets.QPlainTextEdit(self.centralwidget)
        sizePolicy = QtWidgets.QSizePolicy(QtWidgets.QSizePolicy.Expanding, QtWidgets.QSizePolicy.Fixed)
        sizePolicy.setHorizontalStretch(0)
        sizePolicy.setVerticalStretch(0)
        sizePolicy.setHeightForWidth(self.plainTextEdit.sizePolicy().hasHeightForWidth())
        self.plainTextEdit.setSizePolicy(sizePolicy)
        self.plainTextEdit.setMaximumSize(QtCore.QSize(16777215, 100))
        font = QtGui.QFont()
        font.setPointSize(12)
        self.plainTextEdit.setFont(font)
        self.plainTextEdit.setObjectName("plainTextEdit")
        self.verticalLayout.addWidget(self.plainTextEdit)
        self.verticalLayout_2.addLayout(self.verticalLayout)
        self.horizontalLayout_2 = QtWidgets.QHBoxLayout()
        self.horizontalLayout_2.setObjectName("horizontalLayout_2")
        self.pushButton_2 = QtWidgets.QPushButton(self.centralwidget)
        sizePolicy = QtWidgets.QSizePolicy(QtWidgets.QSizePolicy.Fixed, QtWidgets.QSizePolicy.Fixed)
        sizePolicy.setHorizontalStretch(0)
        sizePolicy.setVerticalStretch(0)
        sizePolicy.setHeightForWidth(self.pushButton_2.sizePolicy().hasHeightForWidth())
        self.pushButton_2.setSizePolicy(sizePolicy)
        self.pushButton_2.setObjectName("pushButton_2")
        self.horizontalLayout_2.addWidget(self.pushButton_2)
        self.pushButton = QtWidgets.QPushButton(self.centralwidget)
        sizePolicy = QtWidgets.QSizePolicy(QtWidgets.QSizePolicy.MinimumExpanding, QtWidgets.QSizePolicy.Fixed)
        sizePolicy.setHorizontalStretch(0)
        sizePolicy.setVerticalStretch(0)
        sizePolicy.setHeightForWidth(self.pushButton.sizePolicy().hasHeightForWidth())
        self.pushButton.setSizePolicy(sizePolicy)
        self.pushButton.setObjectName("pushButton")
        self.horizontalLayout_2.addWidget(self.pushButton)
        self.verticalLayout_2.addLayout(self.horizontalLayout_2)
        mainWindow.setCentralWidget(self.centralwidget)
        self.statusbar = QtWidgets.QStatusBar(mainWindow)
        self.statusbar.setObjectName("statusbar")
        mainWindow.setStatusBar(self.statusbar)

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

        self.pushButton.clicked.connect(self.send_message)
        self.pushButton_2.clicked.connect(self.send_message)

    def retranslateUi(self, mainWindow):
        _translate = QtCore.QCoreApplication.translate
        mainWindow.setWindowTitle(_translate("mainWindow", "MainWindow"))
        self.pushButton_2.setText(_translate("mainWindow", "Quit Channel"))
        self.pushButton.setText(_translate("mainWindow", "Send"))

    def send_message(self):
        message = self.plainTextEdit.toPlainText()
        # Here add sending 'message' variable to the server

        if message.strip(' ') != '':
            self.textBrowser.append(message)
        self.plainTextEdit.clear()

    def enter_handler(self, event):
        print(event.key())
        if event.key() == QtCore.Qt.Key_Enter:
            self.send_message()
        else:
            keyPressEvent(qKeyEvent)
        event.accept()

    def escape_handler(self, e):
        if e.key() == QtCore.Qt.Key_Escape:
            self.close()


if __name__ == "__main__":
    app = QtWidgets.QApplication(sys.argv)
    mainWindow = QtWidgets.QMainWindow()
    ui = Ui_mainWindow()
    ui.setupUi(mainWindow)
    mainWindow.show()
    sys.exit(app.exec_())

Answer 1

Qt Designer does not generate a class that is a widget but a class that serves to fill a widget so you can not handle those events from Ui_mainWindow, instead you must create another class that does inherit the appropriate widget. For more information read:

• Using the Generated Code
• https://stackoverflow.com/a/46545116/6622587

To catch the enter there are at least the following methods:

• Override the keyPressEvent method of the QPlainTextEdit.
• Use an eventFilter so that the QPlainTextEdit events are listened to by another class.

I use the eventFilter method because it fits more for your code:

import sys
from PyQt5 import QtCore, QtGui, QtWidgets


class Ui_mainWindow(object):
    def setupUi(self, mainWindow):
        mainWindow.setObjectName("mainWindow")
        mainWindow.resize(406, 686)
        self.centralwidget = QtWidgets.QWidget(mainWindow)
        self.centralwidget.setObjectName("centralwidget")
        self.verticalLayout_2 = QtWidgets.QVBoxLayout(self.centralwidget)
        self.verticalLayout_2.setObjectName("verticalLayout_2")
        self.verticalLayout = QtWidgets.QVBoxLayout()
        self.verticalLayout.setObjectName("verticalLayout")
        self.textBrowser = QtWidgets.QTextBrowser(self.centralwidget)
        font = QtGui.QFont()
        font.setPointSize(13)
        font.setBold(False)
        font.setWeight(50)
        self.textBrowser.setFont(font)
        self.textBrowser.setObjectName("textBrowser")
        self.verticalLayout.addWidget(self.textBrowser)
        self.plainTextEdit = QtWidgets.QPlainTextEdit(self.centralwidget)
        sizePolicy = QtWidgets.QSizePolicy(QtWidgets.QSizePolicy.Expanding, QtWidgets.QSizePolicy.Fixed)
        sizePolicy.setHorizontalStretch(0)
        sizePolicy.setVerticalStretch(0)
        sizePolicy.setHeightForWidth(self.plainTextEdit.sizePolicy().hasHeightForWidth())
        self.plainTextEdit.setSizePolicy(sizePolicy)
        self.plainTextEdit.setMaximumSize(QtCore.QSize(16777215, 100))
        font = QtGui.QFont()
        font.setPointSize(12)
        self.plainTextEdit.setFont(font)
        self.plainTextEdit.setObjectName("plainTextEdit")
        self.verticalLayout.addWidget(self.plainTextEdit)
        self.verticalLayout_2.addLayout(self.verticalLayout)
        self.horizontalLayout_2 = QtWidgets.QHBoxLayout()
        self.horizontalLayout_2.setObjectName("horizontalLayout_2")
        self.pushButton_2 = QtWidgets.QPushButton(self.centralwidget)
        sizePolicy = QtWidgets.QSizePolicy(QtWidgets.QSizePolicy.Fixed, QtWidgets.QSizePolicy.Fixed)
        sizePolicy.setHorizontalStretch(0)
        sizePolicy.setVerticalStretch(0)
        sizePolicy.setHeightForWidth(self.pushButton_2.sizePolicy().hasHeightForWidth())
        self.pushButton_2.setSizePolicy(sizePolicy)
        self.pushButton_2.setObjectName("pushButton_2")
        self.horizontalLayout_2.addWidget(self.pushButton_2)
        self.pushButton = QtWidgets.QPushButton(self.centralwidget)
        sizePolicy = QtWidgets.QSizePolicy(QtWidgets.QSizePolicy.MinimumExpanding, QtWidgets.QSizePolicy.Fixed)
        sizePolicy.setHorizontalStretch(0)
        sizePolicy.setVerticalStretch(0)
        sizePolicy.setHeightForWidth(self.pushButton.sizePolicy().hasHeightForWidth())
        self.pushButton.setSizePolicy(sizePolicy)
        self.pushButton.setObjectName("pushButton")
        self.horizontalLayout_2.addWidget(self.pushButton)
        self.verticalLayout_2.addLayout(self.horizontalLayout_2)
        mainWindow.setCentralWidget(self.centralwidget)
        self.statusbar = QtWidgets.QStatusBar(mainWindow)
        self.statusbar.setObjectName("statusbar")
        mainWindow.setStatusBar(self.statusbar)

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

    def retranslateUi(self, mainWindow):
        _translate = QtCore.QCoreApplication.translate
        mainWindow.setWindowTitle(_translate("mainWindow", "MainWindow"))
        self.pushButton_2.setText(_translate("mainWindow", "Quit Channel"))
        self.pushButton.setText(_translate("mainWindow", "Send"))


class MainWindow(QtWidgets.QMainWindow):
    def __init__(self, parent=None):
        super(MainWindow, self).__init__(parent)
        self.ui = Ui_mainWindow()
        self.ui.setupUi(self)
        self.ui.pushButton.clicked.connect(self.send_message)
        self.ui.pushButton_2.clicked.connect(self.send_message)

        self.ui.plainTextEdit.installEventFilter(self)

    def send_message(self):
        message = self.ui.plainTextEdit.toPlainText()
        # Here add sending 'message' variable to the server
        if message.strip(" ") != "":
            self.ui.textBrowser.append(message)
        self.ui.plainTextEdit.clear()

    def eventFilter(self, obj, event):
        if self.ui.plainTextEdit is obj and event.type() == QtCore.QEvent.KeyPress:
            if event.key() in (QtCore.Qt.Key_Enter, QtCore.Qt.Key_Return):
                self.send_message()
                return True
        return super(MainWindow, self).eventFilter(obj, event)


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