Translations:Manual:Creating parametric objects/9/en

Then, the second important part is the execute method. Any code in this method will be executed when the object is marked to be recomputed, which will happen when a property has been changed. That is all there is to it. Inside execute, you need to do all that needs to be done, that is, calculating a new shape, and attributing to the object itself with something like obj.Shape = myNewShape. That is why the execute method takes an "obj" argument, which will be the FreeCAD document object itself, so we can manipulate it inside our python code.