Many modern programming languages are backed up by a set of libraries (commonly referred as toolkits) for creating GUI applications such as Qt, Tcl/Tk, wxWidgets. PySide is a Python binding of the cross-platform GUI toolkit Qt, and runs on all platforms supported by Qt including Windows, Mac OS X, and Linux. It is one of the alternatives used for GUI programming in Python to Tkinter.

PySide combines the advantages of Qt and Python. A PySide programmer has all the power of Qt, but is able to exploit it with the simplicity of Python. PySide is licensed under the LGPL Version 2.1 license, allowing both free/open source software and proprietary software development. PySide is evolving continuously as any other open source product and you are free to contribute to its development. Some of the applications such as Matplotlib, PhotoGrabber, Wing IDE, Lucas Chess, Fminer, and certify the wide spread usage of PySide in the software industry.

There is some good news for mobile developers. Qt Mobility is a project creating a new suite of Qt APIs for mobile device functionality. The project "PySide Mobility" is a set of bindings that allows Python to access Qt Mobility API. So, learning PySide will also help you in learning mobile development. Come on, let's get started!