PyQt is a Python interface for a cross-platform GUI toolkit named Qt, a project currently developed and maintained by a British firm named Riverbank Computing.

PyQt, with several hundred classes and thousands of functions, is perhaps the most fully featured GUI library currently available for GUI programming in Python. However, this feature load brings in a lot of complexity and a steep learning curve.

Qt, and hence pyQt, has a very rich set of supported widgets. In addition to this, it includes built-in support for network programming, SQL databases, threads, multimedia frameworks, regular expressions, XML, SVG, and much more. The designer feature of Qtletsus generates GUI code from a WYSIWYG (what you see is what you get) interface.

PyQt is available under a variety of licenses, including GNU, General Public License (GPL), and a commercial license. However, its greatest disadvantage is that unlike Qt, it is unavailable under the Lesser General Public License (LGPL).