CadQuery selector strings allow filtering various types of object lists. Most commonly, Edges, Faces, and Vertices are used, but all objects types can be filtered.
Object lists are created by using the following methods, which each collect a type of shape:
Each of these methods accepts either a Selector object or a string. String selectors are simply shortcuts for using the full object equivalents. If you pass one of the string patterns in, CadQuery will automatically use the associated selector object.
Note
String selectors are simply shortcuts to concrete selector classes, which you can use or extend. For a full description of how each selector class works, see :ref:`classreference`.
If you find that the built-in selectors are not sufficient, you can easily plug in your own. See :ref:`extending` to see how.
Selectors can be combined logically, currently defined operators include and, or, not and exc[ept] (set difference). For example:
.. cadquery::
result = cq.Workplane("XY").box(2, 2, 2).edges("|Z and >Y").chamfer(0.2)
Much more complex expressions are possible as well:
.. cadquery::
result = (
cq.Workplane("XY")
.box(2, 2, 2)
.faces(">Z")
.shell(-0.2)
.faces(">Z")
.edges("not(<X or >X or <Y or >Y)")
.chamfer(0.1)
)
All types of string selectors work on faces. In most cases, the selector refers to the direction of the normal vector of the face.
Warning
If a face is not planar, selectors are evaluated at the center of mass of the face. This can lead to results that are quite unexpected.
The axis used in the listing below are for illustration: any axis would work similarly in each case.
| Selector | Selects | Selector Class |
|---|---|---|
| +Z | Faces with normal in +z direction | :py:class:`cadquery.DirectionSelector` |
| |Z | Faces with normal parallel to z dir | :py:class:`cadquery.ParallelDirSelector` |
| -X | Faces with normal in neg x direction | :py:class:`cadquery.DirectionSelector` |
| #Z | Faces with normal orthogonal to z dir | :py:class:`cadquery.PerpendicularDirSelector` |
| %Plane | Faces of type plane | :py:class:`cadquery.TypeSelector` |
| >Y | Face farthest in the positive y dir | :py:class:`cadquery.DirectionMinMaxSelector` |
| <Y | Face farthest in the negative y dir | :py:class:`cadquery.DirectionMinMaxSelector` |
| >Y[-2] | 2nd farthest Face normal to the y dir | :py:class:`cadquery.DirectionNthSelector` |
| <Y[0] | 1st closest Face normal to the y dir | :py:class:`cadquery.DirectionNthSelector` |
| >>Y[-2] | 2nd farthest Face in the y dir | :py:class:`cadquery.CenterNthSelector` |
| <<Y[0] | 1st closest Face in the y dir | :py:class:`cadquery.CenterNthSelector` |
The selector usually refers to the direction of the edge.
Warning
Non-linear edges are not selected for any string selectors except type (%) and center (>>). Non-linear edges are never returned when these filters are applied.
The axis used in the listing below are for illustration: any axis would work similarly in each case.
| Selector | Selects | Selector Class |
|---|---|---|
| +Z | Edges aligned in the Z direction | :py:class:`cadquery.DirectionSelector` |
| |Z | Edges parallel to z direction | :py:class:`cadquery.ParallelDirSelector` |
| -X | Edges aligned in neg x direction | :py:class:`cadquery.DirectionSelector` |
| #Z | Edges perpendicular to z direction | :py:class:`cadquery.PerpendicularDirSelector` |
| %Line | Edges of type line | :py:class:`cadquery.TypeSelector` |
| >Y | Edges farthest in the positive y dir | :py:class:`cadquery.DirectionMinMaxSelector` |
| <Y | Edges farthest in the negative y dir | :py:class:`cadquery.DirectionMinMaxSelector` |
| >Y[1] | 2nd closest parallel edge in the positive y dir | :py:class:`cadquery.DirectionNthSelector` |
| <Y[-2] | 2nd farthest parallel edge in the negative y dir | :py:class:`cadquery.DirectionNthSelector` |
| >>Y[-2] | 2nd farthest edge in the y dir | :py:class:`cadquery.CenterNthSelector` |
| <<Y[0] | 1st closest edge in the y dir | :py:class:`cadquery.CenterNthSelector` |
Only a few of the filter types apply to vertices. The location of the vertex is the subject of the filter.
| Selector | Selects | Selector Class |
|---|---|---|
| >Y | Vertices farthest in the positive y dir | :py:class:`cadquery.DirectionMinMaxSelector` |
| <Y | Vertices farthest in the negative y dir | :py:class:`cadquery.DirectionMinMaxSelector` |
| >>Y[-2] | 2nd farthest vertex in the y dir | :py:class:`cadquery.CenterNthSelector` |
| <<Y[0] | 1st closest vertex in the y dir | :py:class:`cadquery.CenterNthSelector` |
It is possible to use user defined vectors as a basis for the selectors. For example:
.. cadquery::
result = cq.Workplane("XY").box(10, 10, 10)
# chamfer only one edge
result = result.edges(">(-1, 1, 0)").chamfer(1)
Is is also possible to use topological relations to select objects. Currently the following methods are supported:
Ancestors allows to select all objects containing currently selected object.
.. cadquery::
result = cq.Workplane("XY").box(10, 10, 10).faces(">Z").edges("<Y")
result = result.ancestors("Face")
Siblings allows to select all objects of the same type as selection that are connected via the specfied kind of elements.
.. cadquery::
result = cq.Workplane("XY").box(10, 10, 10).faces(">Z")
result = result.siblings("Edge")
It is possible to use selectors with :py:class:`cadquery.Shape` and :py:class:`cadquery.Sketch` objects. This includes chaining and combining.
.. cadquery::
box = cq.Solid.makeBox(1,2,3)
# select top and bottom wires
result = box.faces(">Z or <Z").wires()
:py:class:`cadquery.Workplane` and :py:class:`cadquery.Sketch` provide the following special methods that can be used for quick prototyping of selectors when implementing a complete selector via subclassing of :py:class:`cadquery.Selector` is not desirable.
For example, one could use those methods for selecting objects within a certain range of volumes.
.. cadquery::
from cadquery.occ_impl.shapes import box
result = (
cq.Workplane()
.add([box(1,1,i+1).moved(x=2*i) for i in range(5)])
)
# select boxes with volume <= 3
result = result.filter(lambda s: s.Volume() <= 3)
The same can be achieved using sorting.
.. cadquery::
from cadquery.occ_impl.shapes import box
result = (
cq.Workplane()
.add([box(1,1,i+1).moved(x=2*i) for i in range(5)])
)
# select boxes with volume <= 3
result = result.sort(lambda s: s.Volume())[:3]