The Part module deals with the CAD data structures.
At the moment the CAD capabilites of FreeCAD are very limited but it already supports a few basic CAD primitives like plane, box, cylinder, cone, sphere and torus. For all these primitives a user interface exists to create such elements. Moreover there are several additional primitives for which no user interface exists but that can be created over their Python interface. These primitives are circle and line. More primitives will follow.
Basic data structures
To create primitives over the user interface switch to the Part design workbench and click on 'Create primitives...' menu item under the Part menu. This opens a dialog where your are able to define the type of primitive and define further properties depending on the type you have chosen. Then click on the 'Create' button to create such an element.
There are two further primitives that can only be created over the command line. So far there does not exists a user interface for them.
To create a line element switch to the Python console and type in
- add a line element to the document and set its points
A circle can be created in a similar way
doc = App.activeDocument()
c = Part.Circle()
f = doc.addObject("Part::Feature", "Circle")
f.Shape = c.toShape() # create a shape out of the geometry and assign it the shape property of the feature