ComboBox (one column)

This ComboBox prints to the terminal your selection when you change it.

Code used to generate this example

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from gi.repository import Gtk
import sys

distros = [["Select distribution"], ["Fedora"], ["Mint"], ["Suse"]]


class MyWindow(Gtk.ApplicationWindow):

    def __init__(self, app):
        Gtk.Window.__init__(self, title="Welcome to GNOME", application=app)
        self.set_default_size(200, -1)
        self.set_border_width(10)

        # the data in the model, of type string
        listmodel = Gtk.ListStore(str)
        # append the data in the model
        for i in range(len(distros)):
            listmodel.append(distros[i])

        # a combobox to see the data stored in the model
        combobox = Gtk.ComboBox(model=listmodel)

        # a cellrenderer to render the text
        cell = Gtk.CellRendererText()

        # pack the cell into the beginning of the combobox, allocating
        # no more space than needed
        combobox.pack_start(cell, False)
        # associate a property ("text") of the cellrenderer (cell) to a column (column 0)
        # in the model used by the combobox
        combobox.add_attribute(cell, "text", 0)

        # the first row is the active one by default at the beginning
        combobox.set_active(0)

        # connect the signal emitted when a row is selected to the callback
        # function
        combobox.connect("changed", self.on_changed)

        # add the combobox to the window
        self.add(combobox)

    def on_changed(self, combo):
        # if the row selected is not the first one, write its value on the
        # terminal
        if combo.get_active() != 0:
            print("You chose " + str(distros[combo.get_active()][0]) + ".")
        return True


class MyApplication(Gtk.Application):

    def __init__(self):
        Gtk.Application.__init__(self)

    def do_activate(self):
        win = MyWindow(self)
        win.show_all()

    def do_startup(self):
        Gtk.Application.do_startup(self)

app = MyApplication()
exit_status = app.run(sys.argv)
sys.exit(exit_status)

Useful methods for a ComboBox widget

The ComboBox widget is designed around a Model/View/Controller design: the Model stores the data; the View gets change notifications and displays the content of the model; the Controller, finally, changes the state of the model and notifies the view of these changes. For more information and for a list of useful methods for ComboBox see The Model/View/Controller design.

In line 35 the "changed" signal is connected to the callback function on_changed() using widget.connect(signal, callback function). See Signals and callbacks for a more detailed explanation.