combobox signal when specific item selected

Question

I got a GUI built with QtDesigner with a combo box and several tabs. I want to make it so depending on the item selected in the combobox, only certain tabs will be enabled.

Below is an example with a combo box with 4 items and a tab widget with 4 tabs. What I want to do is when '1' is selected, only Tab 1 will be enabled, when '2' is selected then Tab 1 and Tab 2 will be enabled, etc.

from PyQt5 import QtCore, QtGui, QtWidgets

class Ui_MainWindow(object):
    def setupUi(self, MainWindow):
        MainWindow.setObjectName("MainWindow")
        MainWindow.resize(295, 177)
        self.centralwidget = QtWidgets.QWidget(MainWindow)
        self.centralwidget.setObjectName("centralwidget")
        self.formLayout_5 = QtWidgets.QFormLayout(self.centralwidget)
        self.formLayout_5.setObjectName("formLayout_5")
        self.label_5 = QtWidgets.QLabel(self.centralwidget)
        self.label_5.setObjectName("label_5")
        self.formLayout_5.setWidget(0, QtWidgets.QFormLayout.LabelRole, self.label_5)
        self.comboBox = QtWidgets.QComboBox(self.centralwidget)
        self.comboBox.setObjectName("comboBox")
        self.comboBox.addItem("")
        self.comboBox.addItem("")
        self.comboBox.addItem("")
        self.comboBox.addItem("")
        self.formLayout_5.setWidget(0, QtWidgets.QFormLayout.FieldRole, self.comboBox)
        self.tabWidget = QtWidgets.QTabWidget(self.centralwidget)
        self.tabWidget.setObjectName("tabWidget")
        self.tab = QtWidgets.QWidget()
        self.tab.setEnabled(True)
        self.tab.setObjectName("tab")
        self.formLayout_4 = QtWidgets.QFormLayout(self.tab)
        self.formLayout_4.setObjectName("formLayout_4")
        self.label = QtWidgets.QLabel(self.tab)
        self.label.setObjectName("label")
        self.formLayout_4.setWidget(0, QtWidgets.QFormLayout.LabelRole, self.label)
        self.tabWidget.addTab(self.tab, "")
        self.tab_2 = QtWidgets.QWidget()
        self.tab_2.setObjectName("tab_2")
        self.formLayout_3 = QtWidgets.QFormLayout(self.tab_2)
        self.formLayout_3.setObjectName("formLayout_3")
        self.label_2 = QtWidgets.QLabel(self.tab_2)
        self.label_2.setObjectName("label_2")
        self.formLayout_3.setWidget(0, QtWidgets.QFormLayout.LabelRole, self.label_2)
        self.tabWidget.addTab(self.tab_2, "")
        self.tab_3 = QtWidgets.QWidget()
        self.tab_3.setObjectName("tab_3")
        self.formLayout_2 = QtWidgets.QFormLayout(self.tab_3)
        self.formLayout_2.setObjectName("formLayout_2")
        self.label_3 = QtWidgets.QLabel(self.tab_3)
        self.label_3.setObjectName("label_3")
        self.formLayout_2.setWidget(0, QtWidgets.QFormLayout.LabelRole, self.label_3)
        self.tabWidget.addTab(self.tab_3, "")
        self.tab_4 = QtWidgets.QWidget()
        self.tab_4.setObjectName("tab_4")
        self.formLayout = QtWidgets.QFormLayout(self.tab_4)
        self.formLayout.setObjectName("formLayout")
        self.label_4 = QtWidgets.QLabel(self.tab_4)
        self.label_4.setObjectName("label_4")
        self.formLayout.setWidget(0, QtWidgets.QFormLayout.LabelRole, self.label_4)
        self.tabWidget.addTab(self.tab_4, "")
        self.formLayout_5.setWidget(2, QtWidgets.QFormLayout.SpanningRole, self.tabWidget)
        MainWindow.setCentralWidget(self.centralwidget)
        self.menubar = QtWidgets.QMenuBar(MainWindow)
        self.menubar.setGeometry(QtCore.QRect(0, 0, 295, 26))
        self.menubar.setObjectName("menubar")
        MainWindow.setMenuBar(self.menubar)
        self.statusbar = QtWidgets.QStatusBar(MainWindow)
        self.statusbar.setObjectName("statusbar")
        MainWindow.setStatusBar(self.statusbar)

        self.retranslateUi(MainWindow)
        self.tabWidget.setCurrentIndex(0)
        QtCore.QMetaObject.connectSlotsByName(MainWindow)

    def retranslateUi(self, MainWindow):
        _translate = QtCore.QCoreApplication.translate
        MainWindow.setWindowTitle(_translate("MainWindow", "MainWindow"))
        self.label_5.setText(_translate("MainWindow", "ComboBox"))
        self.comboBox.setItemText(0, _translate("MainWindow", "1"))
        self.comboBox.setItemText(1, _translate("MainWindow", "2"))
        self.comboBox.setItemText(2, _translate("MainWindow", "3"))
        self.comboBox.setItemText(3, _translate("MainWindow", "4"))
        self.label.setText(_translate("MainWindow", "Some text."))
        self.tabWidget.setTabText(self.tabWidget.indexOf(self.tab), _translate("MainWindow", "Tab 1"))
        self.label_2.setText(_translate("MainWindow", "Some text."))
        self.tabWidget.setTabText(self.tabWidget.indexOf(self.tab_2), _translate("MainWindow", "Tab 2"))
        self.label_3.setText(_translate("MainWindow", "Some text."))
        self.tabWidget.setTabText(self.tabWidget.indexOf(self.tab_3), _translate("MainWindow", "Tab 3"))
        self.label_4.setText(_translate("MainWindow", "Some text."))
        self.tabWidget.setTabText(self.tabWidget.indexOf(self.tab_4), _translate("MainWindow", "Tab 4"))


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_())

Answer 1

You have to use the currentIndexChanged signal to get the selected index, then you have to iterate over the tabs setting which should be enabled or not using setTabEnabled():

from PyQt5 import QtCore, QtGui, QtWidgets

class Ui_MainWindow(object):
    # ...


# https://www.riverbankcomputing.com/static/Docs/PyQt5/designer.html#using-the-generated-code
class MainWindow(QtWidgets.QMainWindow, Ui_MainWindow):
    def __init__(self, parent=None):
        super(MainWindow, self).__init__(parent)
        self.setupUi(self)
        self.comboBox.currentIndexChanged.connect(self.onCurrentIndexChanged)
        self.onCurrentIndexChanged(self.comboBox.currentIndex())

    @QtCore.pyqtSlot(int)
    def onCurrentIndexChanged(self, index):
        for i in range(self.tabWidget.count()):
            self.tabWidget.setTabEnabled(i, index >= i)


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