The PySide application can be executed under different platforms/flavors of operating systems. The GUI style of each flavor may vary in representing the application. If you require your application to look good on all platforms, you have to style your application in a way that is native to the operating system. Qt contains a set of style classes that emulate the styles of the different platforms. The abstract class that performs this in Qt is the PySide.QtGui.QStyle class. The classes that inherit this class and provide various style options are QCommonStyle, QWindowsStyle, QPlastiqueStyle, QCleanlooksStyle, QGtkStyle, QMotifStyle, and QCDEStyle. Qt's built-in widgets use QStyle to perform nearly all of their drawing, ensuring that they look exactly like the equivalent native widgets. As an example, the following screenshot contains the different representation of combobox in eight different styles under various OS platforms:

By default, Qt will choose the most appropriate style...