# String Selectors Reference¶

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.

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 CadQuery Class Summary.

If you find that the built-in selectors are not sufficient, you can easily plug in your own. See Extending CadQuery to see how.

## Combining Selectors¶

Selectors can be combined logically, currently defined operators include and, or, not and exc[ept] (set difference). For example:

result = (
cq.Workplane("XY")
.box(2, 2, 2)
.edges("|Z and >Y")
.chamfer(0.2)
)


Much more complex expressions are possible as well:

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)
)


## Filtering Faces¶

All types of string selectors work on faces. In most cases, the selector refers to the direction of the normal vector of the face.

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

cadquery.DirectionSelector

|Z

Faces with normal parallel to z dir

cadquery.ParallelDirSelector

-X

Faces with normal in neg x direction

cadquery.DirectionSelector

#Z

Faces with normal orthogonal to z dir

cadquery.PerpendicularDirSelector

%Plane

Faces of type plane

cadquery.TypeSelector

>Y

Face farthest in the positive y dir

cadquery.DirectionMinMaxSelector

<Y

Face farthest in the negative y dir

cadquery.DirectionMinMaxSelector

>Y[-2]

2nd farthest Face normal to the y dir

cadquery.DirectionNthSelector

<Y[0]

1st closest Face normal to the y dir

cadquery.DirectionNthSelector

>>Y[-2]

2nd farthest Face in the y dir

cadquery.CenterNthSelector

<<Y[0]

1st closest Face in the y dir

cadquery.CenterNthSelector

## Filtering Edges¶

The selector usually refers to the direction of the edge.

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

cadquery.DirectionSelector

|Z

Edges parallel to z direction

cadquery.ParallelDirSelector

-X

Edges aligned in neg x direction

cadquery.DirectionSelector

#Z

Edges perpendicular to z direction

cadquery.PerpendicularDirSelector

%Line

Edges of type line

cadquery.TypeSelector

>Y

Edges farthest in the positive y dir

cadquery.DirectionMinMaxSelector

<Y

Edges farthest in the negative y dir

cadquery.DirectionMinMaxSelector

>Y[1]

2nd closest parallel edge in the positive y dir

cadquery.DirectionNthSelector

<Y[-2]

2nd farthest parallel edge in the negative y dir

cadquery.DirectionNthSelector

>>Y[-2]

2nd farthest edge in the y dir

cadquery.CenterNthSelector

<<Y[0]

1st closest edge in the y dir

cadquery.CenterNthSelector

## Filtering Vertices¶

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

cadquery.DirectionMinMaxSelector

<Y

Vertices farthest in the negative y dir

cadquery.DirectionMinMaxSelector

>>Y[-2]

2nd farthest vertex in the y dir

cadquery.CenterNthSelector

<<Y[0]

1st closest vertex in the y dir

cadquery.CenterNthSelector

## User-defined Directions¶

It is possible to use user defined vectors as a basis for the selectors. For example:

result = cq.Workplane("XY").box(10, 10, 10)

# chamfer only one edge
result = result.edges('>(-1, 1, 0)').chamfer(1)