Question

I’d like to create a GUI app with some buttons and want to handle button press events in same way (i.e. single event handle for all key presses). But I don’t understand how can button_hanlder understand which button was pressed.

Here is code

from PyQt4 import QtCore, QtGui

try:
    _fromUtf8 = QtCore.QString.fromUtf8
except AttributeError:
    _fromUtf8 = lambda s: s

class Ui_MainWindow(object):
    def setupUi(self, MainWindow):
        MainWindow.setObjectName(_fromUtf8("MainWindow"))
        MainWindow.resize(800, 600)
        self.centralwidget = QtGui.QWidget(MainWindow)
        self.centralwidget.setObjectName(_fromUtf8("centralwidget"))
        self.pushButton = QtGui.QPushButton(self.centralwidget)
        self.pushButton.setGeometry(QtCore.QRect(350, 190, 98, 27))
        self.pushButton.setObjectName(_fromUtf8("pushButton"))
        self.pushButton_2 = QtGui.QPushButton(self.centralwidget)
        self.pushButton_2.setGeometry(QtCore.QRect(240, 220, 98, 27))
        self.pushButton_2.setObjectName(_fromUtf8("pushButton_2"))
        self.pushButton_3 = QtGui.QPushButton(self.centralwidget)
        self.pushButton_3.setGeometry(QtCore.QRect(350, 250, 98, 27))
        self.pushButton_3.setObjectName(_fromUtf8("pushButton_3"))
        self.pushButton_4 = QtGui.QPushButton(self.centralwidget)
        self.pushButton_4.setGeometry(QtCore.QRect(460, 220, 98, 27))
        self.pushButton_4.setObjectName(_fromUtf8("pushButton_4"))
        MainWindow.setCentralWidget(self.centralwidget)
        self.menubar = QtGui.QMenuBar(MainWindow)
        self.menubar.setGeometry(QtCore.QRect(0, 0, 800, 25))
        self.menubar.setObjectName(_fromUtf8("menubar"))
        self.menuFile = QtGui.QMenu(self.menubar)
        self.menuFile.setObjectName(_fromUtf8("menuFile"))
        MainWindow.setMenuBar(self.menubar)
        self.statusbar = QtGui.QStatusBar(MainWindow)
        self.statusbar.setObjectName(_fromUtf8("statusbar"))
        MainWindow.setStatusBar(self.statusbar)
        self.menubar.addAction(self.menuFile.menuAction())

        self.retranslateUi(MainWindow)
        QtCore.QObject.connect(self.pushButton_2, QtCore.SIGNAL(_fromUtf8("pressed()")), self.button_handler)
        QtCore.QObject.connect(self.pushButton, QtCore.SIGNAL(_fromUtf8("pressed()")), self.button_handler)
        QtCore.QObject.connect(self.pushButton_4, QtCore.SIGNAL(_fromUtf8("pressed()")), self.button_handler)
        QtCore.QObject.connect(self.pushButton_3, QtCore.SIGNAL(_fromUtf8("pressed()")), self.button_handler)
        QtCore.QMetaObject.connectSlotsByName(MainWindow)

    def retranslateUi(self, MainWindow):
        MainWindow.setWindowTitle(QtGui.QApplication.translate("MainWindow", "MainWindow", None, QtGui.QApplication.UnicodeUTF8))
        self.pushButton.setText(QtGui.QApplication.translate("MainWindow", "Up", None, QtGui.QApplication.UnicodeUTF8))
        self.pushButton_2.setText(QtGui.QApplication.translate("MainWindow", "Right", None, QtGui.QApplication.UnicodeUTF8))
        self.pushButton_3.setText(QtGui.QApplication.translate("MainWindow", "Down", None, QtGui.QApplication.UnicodeUTF8))
        self.pushButton_4.setText(QtGui.QApplication.translate("MainWindow", "Left", None, QtGui.QApplication.UnicodeUTF8))
        self.menuFile.setTitle(QtGui.QApplication.translate("MainWindow", "File", None, QtGui.QApplication.UnicodeUTF8))

    def button_handler(self):
        # Which button was pressed?

if __name__ == "__main__":
    import sys
    app = QtGui.QApplication(sys.argv)
    MainWindow = QtGui.QMainWindow()
    ui = Ui_MainWindow()
    ui.setupUi(MainWindow)
    MainWindow.show()
    sys.exit(app.exec_())

I want in button_handler determine which button was pressed, for example by button caption.

Answer 1

The QButtonGroup is designed for this. It will work with any kind of button which inherits QAbstractButton, such as QPushButton, QRadioButton, QCheckBox, etc.

Just add all the buttons to the button-group using addButton and then connect the buttonClicked signal to a handler.

NB: It may be a good idea to put all the buttons inside a container widget, such as a QGroupBox, QFrame or just a plain QWidget. This will allow you to loop over the container’s children and automatically add all the buttons to a button-group.

Example Code:

btngroup.py:

from PyQt4 import QtGui, QtCore
from btngroup_ui import Ui_ButtonGroup

class Window(QtGui.QWidget, Ui_ButtonGroup):
    def __init__(self):
        QtGui.QWidget.__init__(self)
        self.setupUi(self)
        self.buttonGroup = QtGui.QButtonGroup(self)
        for button in self.buttonBox.findChildren(QtGui.QAbstractButton):
            self.buttonGroup.addButton(button)
        self.buttonGroup.buttonClicked.connect(self.handleButtonClicked)

    def handleButtonClicked(self, button):
        print('"%s" was clicked' % button.text())

if __name__ == '__main__':

    import sys
    app = QtGui.QApplication(sys.argv)
    window = Window()
    window.show()
    sys.exit(app.exec_())

btngroup_ui.py:

# -*- coding: utf-8 -*-

# Form implementation generated from reading ui file 'btngroup.ui'
#
# Created: Wed Nov 21 17:50:42 2012
#      by: PyQt4 UI code generator 4.9.5
#
# WARNING! All changes made in this file will be lost!

from PyQt4 import QtCore, QtGui

try:
    _fromUtf8 = QtCore.QString.fromUtf8
except AttributeError:
    _fromUtf8 = lambda s: s

class Ui_ButtonGroup(object):
    def setupUi(self, ButtonGroup):
        ButtonGroup.setObjectName(_fromUtf8("ButtonGroup"))
        ButtonGroup.resize(240, 167)
        self.horizontalLayout = QtGui.QHBoxLayout(ButtonGroup)
        self.horizontalLayout.setObjectName(_fromUtf8("horizontalLayout"))
        self.buttonBox = QtGui.QWidget(ButtonGroup)
        self.buttonBox.setObjectName(_fromUtf8("buttonBox"))
        self.verticalLayout = QtGui.QVBoxLayout(self.buttonBox)
        self.verticalLayout.setMargin(0)
        self.verticalLayout.setObjectName(_fromUtf8("verticalLayout"))
        self.buttonA = QtGui.QPushButton(self.buttonBox)
        self.buttonA.setObjectName(_fromUtf8("buttonA"))
        self.verticalLayout.addWidget(self.buttonA)
        self.buttonB = QtGui.QPushButton(self.buttonBox)
        self.buttonB.setObjectName(_fromUtf8("buttonB"))
        self.verticalLayout.addWidget(self.buttonB)
        self.buttonC = QtGui.QPushButton(self.buttonBox)
        self.buttonC.setObjectName(_fromUtf8("buttonC"))
        self.verticalLayout.addWidget(self.buttonC)
        self.buttonD = QtGui.QPushButton(self.buttonBox)
        self.buttonD.setObjectName(_fromUtf8("buttonD"))
        self.verticalLayout.addWidget(self.buttonD)
        self.horizontalLayout.addWidget(self.buttonBox)

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

    def retranslateUi(self, ButtonGroup):
        ButtonGroup.setWindowTitle(QtGui.QApplication.translate("ButtonGroup", "Button Group", None, QtGui.QApplication.UnicodeUTF8))
        self.buttonA.setText(QtGui.QApplication.translate("ButtonGroup", "Button A", None, QtGui.QApplication.UnicodeUTF8))
        self.buttonB.setText(QtGui.QApplication.translate("ButtonGroup", "Button B", None, QtGui.QApplication.UnicodeUTF8))
        self.buttonC.setText(QtGui.QApplication.translate("ButtonGroup", "Button C", None, QtGui.QApplication.UnicodeUTF8))
        self.buttonD.setText(QtGui.QApplication.translate("ButtonGroup", "Button D", None, QtGui.QApplication.UnicodeUTF8))