PyGTK - Introduction

PyGTK is a set of wrappers written in Python and C for GTK + GUI library. It is part of the GNOME project. It offers comprehensive tools for building desktop applications in Python. Python bindings for other popular GUI libraries are also available.
PyQt is a Python port of QT library. Our PyQt tutorial can be found here. Similarly, wxPython toolkit is Python binding for wxWidgets, another popular cross-platform GUI library. Our wxPython tutorial is available here.

PyGTK - Environment

PyGTK for Microsoft Windows

The installation of PyGTK for Microsoft Windows involves the following steps −

• Step 1 − Install a 32-bit Python interpreter (latest Python 2.7 distribution)
• Step 2 − Download and install GTK+ runtime.
  

PyGTK - Hello World

Creating a window using PyGTK is very simple. To proceed, we first need to import the gtk module in our code.

import gtk

The gtk module contains the gtk.Window class. Its object constructs a toplevel window. We derive a class from gtk.Window.

class PyApp(gtk.Window):

PyGTK - Important Classes

The PyGTK module contains various widgets. gtk.Object class acts as the base class for most of the widgets as well as for some non-widget classes. The toplevel window for desktop applications using PyGTK is provided by gtk.Window class. The following table lists the important widgets and their functions −

PyGTK - Window Class

An object of the gtk.Window class provides a widget that users commonly think of as a Wwindow. This widget is a container hence, it can hold one child widget. It provides a displayable area decorated with title bar and resizing controls.
gtk.Window class has the following constructor −

PyGTK - Button Class

The gtk.Button widget is usually displayed as a pushbutton with a text label. It is generally used to attach a callback function or method that is called when the button is clicked.
The gtk.Button class has the following constructor −

gtk.Button(label = None, stock = None, use_underline = True)

Wherein,

PyGTK - Label Class

A Label widget is useful to display non-editable text. Label is used by many other widgets internally. For example, Button has a label to show text on the face. Similarly, MenuItem objects have a label. A label is a windowless object, so it cannot receive events directly.
Label class has a simple constructor −

PyGTK - Entry Class

Entry widget is a single-line text entry widget. If the entered text is longer than the allocation of the widget, the widget will scroll so that the cursor position is visible.
Entry field can be converted in password mode using set_visibility() method of this class. Entered text is substituted by character chosen by invisible_char() method, default being '*'.
The Entry class has the following constructor −

PyGTK - Signal Handling

Unlike a console mode application, which is executed in a sequential manner, a GUI-based application is event driven. The gtk.main() function starts an infinite loop. Events occurring on the GUI are transferred to appropriate callback functions.

PyGTK - Event Handling

In addition to the signal mechanism, window system events can also be connected to callback functions. Window resizing, key press, scroll event etc. are some of common window system events. These events are reported to application's main loop. From there, they are passed along via signals to the callback functions.
Some of the system events are listed below −

PyGTK - Containers

PyGTK library provides different container classes to control the placement of widgets inside a window. The easiest way is to use a fixed container class and place a widget inside it by specifying its absolute coordinates measured in pixels.
Let us now follow these steps −

PyGTK - Box Class

The gtk.Box class is an abstract class defining the functionality of a container in which widgets are placed in a rectangular area. gtk.HBox and gtk.VBox widgets are derived from it.
Child widgets in gtk.Hbox are arranged horizontally in the same row. On the other hand, child widgets of gtk.VBox are arranged vertically in the same column.

PyGTK - ButtonBox Class

The ButtonBox class in gtk API serves as a base class for containers to hold multiple buttons either horizontally or vertically. Two subclasses HButtonBox and VButtonBox are derived from the ButtonBox class, which itself is a subclass of gtk.Box class.

PyGTK - Alignment Class

This widget proves useful in controlling alignment and size of its child widgets. It has four properties called xalign, yalign, xscale and yscale. The scale properties specify how much of free space will be used by the child widgets. The align properties areused to place the child widget within available area.

PyGTK - EventBox Class

Some widgets in PyGTK tool kit do not have their own window. Such windowless widgets cannot receive event signals. Such widgets, for example a label, if put inside an eventbox can receive signals.
EventBox is an invisible container that provides window to windowless widgets. It has a simple constructor without any argument −

gtk.EventBox()

PyGTK - Layout Class

The gtk.Layout is a container widget similar to gtk.Fixed. Widgets are placed in Layout widget by specifying absolute coordinates. However, the Layout differs from fixed widget in the following ways −

• The layout widget can have infinite width and height. The maximum value of width and height is limited by the size of unsigned integer.
  

PyGTK - ComboBox Class

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.

PyGTK - ToggleButton Class

ToggleButton widget is a gtk.Button with two states — a pressed or active (or on) state and a normal or inactive (or off) state. Every time the button is pressed, the state alternates. The state of the ToggleButton can also be changed programmatically by set_active() method. To switch the state of the button, the toggled() method is also available.

PyGTK - CheckButton Class

A CheckButton widget is nothing but a ToggleButton styled as a checkbox and a label. It inherits all properties and methods from the ToggleButton class. Unlike ToggleButton where the caption is on the button's face, a CheckButton displays a small square which is checkable and has a label to its right.
Constructor, methods, and signals associated with gtk.CheckButton are exactly the same as gtk.ToggleButton.

PyGTK - RadioButton Class

A single RadioButton widget offers functionality similar to CheckButton. However, when more than one radio button is present in the same container, then a mutually exclusive choice is available for the user to choose from one of the available options. If every radio button in the container belongs to the same group, then as one is selected, others are automatically deselected.