PyQt - Major Classes


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PyQt API is a large collection of classes and methods. These classes are defined in more than 20 modules. Following are some of the frequently used modules −

Sr.No. Modules & Description
1

QtCore

Core non-GUI classes used by other modules

2

QtGui

Graphical user interface components

3

QtMultimedia

Classes for low-level multimedia programming

4

QtNetwork

Classes for network programming

5

QtOpenGL

OpenGL support classes

6

QtScript

Classes for evaluating Qt Scripts

7

QtSql

Classes for database integration using SQL

8

QtSvg

Classes for displaying the contents of SVG files

9

QtWebKit

Classes for rendering and editing HTML

10

QtXml

Classes for handling XML

11

QtAssistant

Support for online help

12

QtDesigner

Classes for extending Qt Designer

PyQt API contains more than 400 classes. The QObject class is at the top of class hierarchy. It is the base class of all Qt objects. Additionally, QPaintDevice class is the base class for all objects that can be painted.

QApplication class manages the main settings and control flow of a GUI application. It contains main event loop inside which events generated by window elements and other sources are processed and dispatched. It also handles system-wide and application-wide settings.

QWidget class, derived from QObject and QPaintDevice classes is the base class for all user interface objects. QDialog and QFrame classes are also derived from QWidget class. They have their own sub-class system.

Following diagrams depict some important classes in their hierarchy.

Hierarchy QWidget QDialog QIODevice QPaintDevice

Here is a select list of frequently used widgets −

Sr.No. Widgets & Description
1

QLabel

Used to display text or image

2

QLineEdit

Allows the user to enter one line of text

3

QTextEdit

Allows the user to enter multi-line text

4

QPushButton

A command button to invoke action

5

QRadioButton

Enables to choose one from multiple options

6

QCheckBox

Enables choice of more than one options

7

QSpinBox

Enables to increase/decrease an integer value

8

QScrollBar

Enables to access contents of a widget beyond display aperture

9

QSlider

Enables to change the bound value linearly.

10

QComboBox

Provides a dropdown list of items to select from

11

QMenuBar

Horizontal bar holding QMenu objects

12

QStatusBar

Usually at bottom of QMainWindow, provides status information.

13

QToolBar

Usually at top of QMainWindow or floating. Contains action buttons

14

QListView

Provides a selectable list of items in ListMode or IconMode

15

QPixmap

Off-screen image representation for display on QLabel or QPushButton object

16

QDialog

Modal or modeless window which can return information to parent window

A typical GUI based application’s top level window is created by QMainWindow widget object. Some widgets as listed above take their appointed place in this main window, while others are placed in the central widget area using various layout managers.

The following diagram shows the QMainWindow framework −

QMainWindow
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