# Introduction

This is the reference guide for PyQt4 4.12.1. PyQt4 is a set of Python bindings for v4 and v5 of the Qt application framework from Digia.

There is a separate PyQt4 Class Reference.

Qt is a set of C++ libraries and development tools that includes platform independent abstractions for graphical user interfaces, networking, threads, Unicode, regular expressions, SQL databases, SVG, OpenGL, XML, and user and application settings. PyQt4 implements 440 of these classes as a set of Python modules.

PyQt4 supports the Windows, Linux, UNIX and MacOS/X platforms.

PyQt4 does not include Qt itself - you must obtain it separately.

The homepage for PyQt4 is http://www.riverbankcomputing.com/software/pyqt/. Here you will always find the latest stable version, current development previews, and the latest version of this documentation.

PyQt4 is built using the SIP bindings generator. SIP must be installed in order to build and use PyQt4.

Earlier versions of Qt are supported by PyQt v3.

## License

PyQt4 is dual licensed on all platforms under the Riverbank Commercial License and the GPL v3. Your PyQt4 license must be compatible with your Qt license. If you use the GPL versions then your own code must also use a compatible license.

PyQt4, unlike Qt, is not available under the LGPL.

You can purchase a commercial PyQt4 license here.

## PyQt4 Components

PyQt4 comprises a number of different components. First of all there are a number of Python extension modules. These are all installed in the `PyQt4` Python package.

- The `QtCore` module. This contains the core non-GUI classes, including the event loop and Qt’s signal and slot mechanism. It also includes platform independent abstractions for Unicode, threads, mapped files, shared memory, regular expressions, and user and application settings.
- The `QtGui` module. This contains the majority of the GUI classes.
- The `QtHelp` module. This contains classes for creating and viewing searchable documentation.
- The `QtNetwork` module. This module contains classes for writing UDP and TCP clients and servers. It includes classes that implement FTP and HTTP clients and support DNS lookups.
- The `QtOpenGL` module. This module contains classes that enable the use of OpenGL in rendering 3D graphics in PyQt4 applications.
- The `QtScript` module. This module contains classes that enable PyQt4 applications to be scripted using Qt’s JavaScript interpreter.
- The `QtScriptTools` module. This module contains classes that contain additional components (e.g. a debugger) that are used with Qt’s JavaScript interpreter.
- The `QtSql` module. This module contains classes that integrate with SQL databases. It includes editable data models for database tables that can be used with GUI classes. It also includes an implementation of SQLite.
- The `QtSvg` module. This module contains classes for displaying the contents of SVG files.
- The `QtTest` module. This module contains functions that enable unit testing of PyQt4 applications. (PyQt4 does not implement the complete Qt unit test framework. Instead it assumes that the standard Python unit test framework will be used and implements those functions that simulate a user interacting with a GUI.)
- The `QtWebKit` module. This module implements a web browser engine based on the WebKit open source browser engine.
- The `QtXml` module. This module contains classes that implement SAX and DOM interfaces to Qt’s XML parser.
- The `QtXmlPatterns` module. This module contains classes that implement XQuery and XPath support for XML and custom data models.
- The `phonon` module. This module contains classes that implement a cross-platform multimedia framework that enables the use of audio and video content in PyQt4 applications.
- The `QtDBus` module. This Unix-only module provides classes that support Inter-Process Communication using the D-Bus protocol.
- The `QtDeclarative` module. This module provides a declarative framework for building highly dynamic, custom user interfaces using QML.
- The `QtMultimedia` module. This module provides low-level multimedia functionality. Application developers would normally use the `phonon` module.
- The `QtAssistant` module. This module contains classes that allow Qt Assistant to be integrated with a PyQt4 application to provide online help. This module is not available with Qt v4.7 and later - use the `QtHelp` module instead.
- The `QtDesigner` module. This module contains classes that allow Qt Designer to be extended using PyQt4. See Writing Qt Designer Plugins for a full description of how to do this.
- The `QAxContainer` module. This Windows-only module contains classes that allow access to ActiveX controls and COM objects.
- The `Qt` module. This module consolidates the classes contained in all of the modules described above into a single module. This has the advantage that you don’t have to worry about which underlying module contains a particular class. It has the disadvantage that it loads the whole of the Qt framework, thereby increasing the memory footprint of an application. Whether you use this consolidated module, or the individual component modules is down to personal taste.
- The DBus support module is installed as `dbus.mainloop.qt`. This module provides support for the Qt event loop in the same way that the `dbus.mainloop.glib` included with the standard `dbus-python` bindings package provides support for the GLib event loop. The API is described in DBus Support. It is only available if the `dbus-python` v0.80 (or later) bindings package is installed. The `QtDBus` module provides a more Qt-like interface to DBus.
- The `uic` module. This module contains classes for handling the `.ui` files created by Qt Designer that describe the whole or part of a graphical user interface. It includes classes that load a `.ui` file and render it directly, and classes that generate Python code from a `.ui` file for later execution.
- The `pyqtconfig` module is an extention of the SIP build system and is created when PyQt4 is configured. It encapsulates all the necessary information about your Qt installation and makes it easier to write installation scripts for bindings built on top of PyQt4. It is covered in detail in The PyQt4 Build System.

PyQt4 also contains a number of utility programs.

- pyuic4 corresponds to the Qt uic utility. It converts GUIs created using Qt Designer to Python code.

- pyrcc4 corresponds to the Qt rcc utility. It embeds arbitrary resources (eg. icons, images, translation files) described by a resource collection file in a Python module.

  Note

  It will only be included if your copy of Qt includes the XML module.

- pylupdate4 corresponds to the Qt lupdate utility. It extracts all of the translatable strings from Python code and creates or updates `.ts` translation files. These are then used by Qt Linguist to manage the translation of those strings.

  Note

  It will only be included if your copy of Qt includes the XML module.

When PyQt4 is configured a file called `PyQt4.api` is generated. This can be used by the QScintilla editor component (at http://www.riverbankcomputing.com/software/qscintilla/) to enable the use of auto-completion and call tips when editing PyQt4 code. The API file is installed automatically if QScintilla is already installed.

PyQt4 includes a large number of examples. These are ports to Python of many of the C++ examples provided with Qt. They can be found in the `examples` directory.

Finally, PyQt4 contains the `.sip` files used by SIP to generate PyQt4 itself. These can be used by developers of bindings of other Qt based class libraries - for example PyQwt and PyQwt3D.