PyGTK - ComboBox Class

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ComboBox is a powerful and popular widget in any GUI toolkit. It provides a dropdown list of items from which a user can choose. The gtk.ComboBox widget implements the CellLayout interface and provides a number of methods to manage the display of items.

The object of gtk.ComboBox class is associated with a ListSore, which is a list model that can be used with widgets that display collection of items. Items are added to ListStore with the append() method. Further, a CellRendererText object is created and packed into the combobox.

Follow these steps to set up a combobox.

combobox = gtk.ComboBox()
store = gtk.ListStore(gobject.TYPE_STRING)
cell = gtk.CellRendererText()
combobox.pack_start(cell)
combobox.add_attribute(cell, 'text', 0)

PyGTK offers a convenience method — gtk.combo_box_new_text() to create a combo box instead of using a list store. Associated convenience methods append_text(), prepend_text(), insert_text() and remove_text() are used to manage the combo boxcontents.

gtk.ComboBox class has the following methods −

Sr.No.	Methods and Description
1	set_wrap_width() Sets the number of columns to be displayed in the popup table layout
2	get_active() Returns the value of the "active" property which is the index in the model of the currently active item
3	set_active() Sets the active item of the combo_box to the item with the model index specified
4	set_model() Sets the model used by the combo box
5	append_text() Appends the string specified by text to the list of strings stored in the combo box list store
6	Insert_text() Inserts the string specified by text in the combo box gtk.ListStore at the index specified by position
7	prepend_text() Prepends the string specified by text to the list of strings stored in the list store
8	remove_text() Removes the string at the index specified by position in the associated liststore
9	get_active_text() Returns the currently active string

The ComboBox widget emits the following signals −

changed	This is emitted when a new item in the combo box is selected
move_active	This is a keybinding signal which gets emitted to move the active selection.
Popdown	This is a keybinding signal which gets emitted to popdown the combo box list. The default bindings for this signal are Alt+Up and Escape
Popup	This is a keybinding signal which gets emitted to popup the combo box list. The default bindings for this signal are Alt+Down.

Two example codes for the demonstration of ComboBox are given below.

Example 1

In this example, a ListStore is populated with the names of popular Python GUI toolkits and it is associated with a ComboBox widget. As a user makes a choice, the changed signal is emitted. It is connected to a callback function to display the user's choice.

import pygtk
pygtk.require('2.0')
import gtk

class PyApp(gtk.Window):
   def __init__(self):
      super(PyApp, self).__init__()
      self.set_title("ComboBox with ListStore")
      self.set_default_size(250, 200)
      self.set_position(gtk.WIN_POS_CENTER)
      
      combobox = gtk.ComboBox()
      store = gtk.ListStore(str)
      cell = gtk.CellRendererText()
      combobox.pack_start(cell)
      combobox.add_attribute(cell, 'text', 0)
      fixed = gtk.Fixed()
      lbl = gtk.Label("select a GUI toolkit")
      fixed.put(lbl, 25,75)
      fixed.put(combobox, 125,75)
      lbl2 = gtk.Label("Your choice is:")
      fixed.put(lbl2, 25,125)
      self.label = gtk.Label("")
      fixed.put(self.label, 125,125)
      self.add(fixed)
      
      store.append (["PyQt"])
      store.append (["Tkinter"])
      store.append (["WxPython"])
      store.append (["PyGTK"])
      store.append (["PySide"])
      combobox.set_model(store)
      combobox.connect('changed', self.on_changed)
      combobox.set_active(0)
      self.connect("destroy", gtk.main_quit)
      self.show_all()
      return
   
   def on_changed(self, widget):
      self.label.set_label(widget.get_active_text())
      return
      if __name__ == '__main__':
PyApp()
gtk.main()

Upon execution, the program displays the following output −

Example 2

The second version of the program uses the convenience method combo_box_new_text() to create a combo box and append_text() function to add strings in it. In both programs, the get_active_text() method is used to fetch user's selection and display on a label on the window.

import gtk
class PyApp(gtk.Window):
   def __init__(self):
      super(PyApp, self).__init__()
      self.set_title("Simple ComboBox")
      self.set_default_size(250, 200)
      self.set_position(gtk.WIN_POS_CENTER)
      
      cb = gtk.combo_box_new_text()
      cb.connect("changed", self.on_changed)
      cb.append_text('PyQt')
      cb.append_text('Tkinter')
      cb.append_text('WxPython')
      cb.append_text('PyGTK')
      cb.append_text('PySide')
      
      fixed = gtk.Fixed()
      lbl = gtk.Label("select a GUI toolkit")
      fixed.put(lbl, 25,75)
      
      fixed.put(cb, 125,75)
      lbl2 = gtk.Label("Your choice is:")
      fixed.put(lbl2, 25,125)
      
      self.label = gtk.Label("")
      fixed.put(self.label, 125,125)
      self.add(fixed)
      self.connect("destroy", gtk.main_quit)
      self.show_all()
   
   def on_changed(self, widget):
      self.label.set_label(widget.get_active_text())
      if __name__ == '__main__':
PyApp()
gtk.main()

The output of this program is similar to that of the previous program.