Template

In early stages of design computing experimentation, not all input and output parameters are known in advance. The recommended setup for this scenario is to prepare the component as seen below.

1. Rename the out parameter to messages and connect a panel component, where you can view standard outputs and errors.
2. Create a geometry output parameter to publish any geometric objects to be displayed in the viewport.

When the specific format and type of output information becomes more clear, it is only a matter of creating new parameters and updating the code as needed.

Template Python Code

You may set the following code snippet as the default python script template by pasting the code below into the python script editor and selecting the Tools / Set Template Code... menu item.

import math, random
from Rhino import RhinoApp, RhinoDoc
from Rhino.Geometry import ( Point3d, Vector3d, Plane, Transform,
    Interval, Point2d, Point3f, Vector3f, Point2f, Line, Circle, Curve,
    Surface, NurbsCurve, NurbsSurface, Brep, Mesh,  Arc, ArcCurve,
    BezierCurve, Box, Cone, ControlPoint, Cylinder, Ellipse, Extrusion,
    LineCurve, LoftType, Point4d, PointCloud, PolyCurve, Polyline,
    PolylineCurve, Quaternion, Sphere )
from Rhino.Geometry.Intersect import Intersection
from System.Drawing import Color

geometry = []
def Add( element ):
    geometry.append( element )

''' Script Below
'''
Add( Point3d( 0, 1, 2 ) )
print( 'done' )

1. The math module is used for accessing built-in mathematics functions such as sin, cos, sqrt, exp etc. See relevant documentation. The random provides random number generators.
2. The RhinoDoc class enables direct manipulation of Rhino's currently opened document. It can be used for loading and saving geometries outside of Grasshopper. See relevant documentation. The RhinoApp class accesses the application itself.
3. The Geometry namespace contains definitions for creating and manipulating points, vectors, curves, surfaces, meshes, breps etc. See relevant documentation
4. The Intersect namespace contains definitions for computing intersections between different kinds of geometries. See relevant documentation.
5. The Color class is used for creating color objects as defined by the .NET system and used by Rhino. See relevant documentation

Annotated Template

It is often useful to visualize text labels at specific points in the viewport. As it is not possible to emit certain types of visuals from python components, we need to adapt the template to output pairs of points and labels and use the Text Tag 3D component. The cluster is used for decoupling the data packed in lists.

import math, random
from Rhino import RhinoApp, RhinoDoc
from Rhino.Geometry import ( Point3d, Vector3d, Plane, Transform,
    Interval, Point2d, Point3f, Vector3f, Point2f, Line, Circle, Curve,
    Surface, NurbsCurve, NurbsSurface, Brep, Mesh,  Arc, ArcCurve,
    BezierCurve, Box, Cone, ControlPoint, Cylinder, Ellipse, Extrusion,
    LineCurve, LoftType, Point4d, PointCloud, PolyCurve, Polyline,
    PolylineCurve, Quaternion, Sphere )
from Rhino.Geometry.Intersect import Intersection
from System.Drawing import Color

geometry = []
def Add( element ):
    geometry.append( element )

annotations = []
def Anno( point, label ):
    annotations.append( [point, label] )

''' Script Below
'''
source = Point3d.Origin
target = Point3d.Origin + Vector3d.XAxis

Anno( source, 's' )
Anno( target, 't' )

Add( Line( source, target ) )

Vectors Template

The template provided below simplifies the process of visualizing vectors. The Vec( ) method can be used to specify the origin and direction as well as the color of a 3D vector, which is then rendered using the Vector Display Ex component. The cluster is used for decoupling the data packed in lists.

import math, random
from Rhino import RhinoApp, RhinoDoc
from Rhino.Geometry import ( Point3d, Vector3d, Plane, Transform,
    Interval, Point2d, Point3f, Vector3f, Point2f, Line, Circle, Curve,
    Surface, NurbsCurve, NurbsSurface, Brep, Mesh,  Arc, ArcCurve,
    BezierCurve, Box, Cone, ControlPoint, Cylinder, Ellipse, Extrusion,
    LineCurve, LoftType, Point4d, PointCloud, PolyCurve, Polyline,
    PolylineCurve, Quaternion, Sphere )
from Rhino.Geometry.Intersect import Intersection
from System.Drawing import Color

geometry = []
def Add( element ):
    geometry.append( element )

vectors = []
def Vec( point, direction, color = Color.Black ):
    vectors.append( [point, direction, color] )

''' Script Below
'''
source = Point3d.Origin
target = Point3d.Origin + Vector3d.XAxis
Vec( source, target - source, Color.Blue )
Add( Line( source, target ) )

Resources

Grasshopper