When comparing pyglet vs PySide, the Slant community recommends PySide for most people. In the question“What are the best Python GUI frameworks/toolkits?” PySide is ranked 7th while pyglet is ranked 10th. The most important reason people chose PySide is:
Qt for Python aka PySide2 is the official set of Python bindings supported by the Qt Company.
Specs
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Pros
Pro 3D support
Since pyglet is so tightly woven with OpenGL it allows the support of drawing in 3D.
Pro Cross-platform
Works with Windows, Linux, and OS X.
Pro Written in pure Python
A small advantage, but being a core Python developer, it may be the best to stick to the roots and develop with pyglet as it is able to compile using other Python interpreters.
Pro Supported by the Qt Company
Qt for Python aka PySide2 is the official set of Python bindings supported by the Qt Company.
Pro Qt widgets
Possibility to use a traditional widget-based user interface.
Pro QtQuick/QML
Possibility to use a declarative approach to define the user interface.
Pro Weak copyleft
PySide is licensed under the LGPL, which makes it easier to incorporate into commercial projects than PyQt.
Cons
Con Small community/popularity
There is a decent amount of documentation and API to go along with pyglet, but in terms of community support there seems to be very little.
Con Similar to PyQt, you need a C++ background. at least you can read C++ code
Qt's document is poor, and Qt for Python(PySdie) is even worse. this document assumes that you are already familiar with Qt. if you want to customize a Widget, you need to look at the Qt C++ source code to know what to do.