From FreeCAD Documentation
Revision as of 21:24, 23 August 2020 by FuzzyBot (talk | contribs) (Updating to match new version of source page)
Jump to navigation Jump to search
Other languages:
Bahasa Indonesia • ‎Deutsch • ‎English • ‎Türkçe • ‎español • ‎français • ‎italiano • ‎polski • ‎português • ‎română • ‎svenska • ‎čeština • ‎русский • ‎日本語


PySide es un enlace Python del conjunto de herramientas GUI multiplataforma Qt. FreeCAD utiliza PySide para todos los fines de la GUI (interfaz de usuario gráfica) dentro de Python. PySide es una alternativa al paquete PyQt que fue utilizado anteriormente por FreeCAD para su GUI. PySide tiene una licencia más permisible. Ver Differences Between PySide and PyQt Para más información sobre las diferencias.

When you install FreeCAD, you should get both Qt and PySide as part of the package. If you are compiling yourself, then you must verify that these two libraries are installed, in order for FreeCAD to run correctly. Of course, PySide will only work if Qt is present.

In the past, FreeCAD used PyQt, another Qt binding for Python, but in 2013 (1dc122dc9a) the project migrated to PySide because it has a more permissible license.

For more information see:

PySideScreenSnapshot1.jpg PySideScreenSnapshot2.jpg

Examples created with PySide. Left: a simple dialog. Right: a more complex dialog with graphs.

PySide in FreeCAD with Qt5

FreeCAD was developed to be used with Python 2 and Qt4. As these two libraries became obsolete, FreeCAD transitioned to Python 3 and Qt5. In most cases this transition was done without needing to break backwards compatibility.

Normally, the PySide module provides support for Qt4, while PySide2 provides support for Qt5. However, in FreeCAD, there is no need to use PySide2 directly, as a special PySide module is included to handle Qt5.

This PySide module is located in the Ext/ directory of an installation of FreeCAD compiled for Qt5.


This module just imports the necessary classes from PySide2, but places them in the PySide namespace. This means that in most cases the same code can be used with both Qt4 and Qt5, as long as it imports the single PySide module.

PySide2.QtCore -> PySide.QtCore
PySide2.QtGui -> PySide.QtGui
PySide2.QtSvg -> PySide.QtSvg
PySide2.QtUiTools -> PySide.QtUiTools

The only unusual aspect is that the PySide2.QtWidgets classes are placed in the PySide.QtGui namespace.

PySide2.QtWidgets.QCheckBox -> PySide.QtGui.QCheckBox


Examples of PySide use

The examples of PySide are divided into 3 parts, differentiated by level of exposure to PySide, Python and the FreeCAD internals. The first page has an overview on PySide; the second and third pages are mostly code examples at different levels.

It is expected that these examples are useful to get started, and afterwards the user can consult other resources online, or the official documentation.



There are some differences in handling of widgets in Qt4 (PySide) and Qt5 (PySide2). The programmer should be aware of these incompatibilities, and should consult the official documentation if something doesn't seem to work as expected on a given platform. Nevertheless, Qt4 is considered obsolete, so most development should target Qt5 and Python 3.

The PySide documentation refers to the Python-style classes; however, since Qt is originally a C++ library, the same information should be available in the corresponding C++ reference.