If you have one connected edge loop, you can use this script.
The mesh object has to be selected before executing the script.
obj = bpy.context.active_object
if (None == obj):
if (obj.type != 'MESH'):
edgesA = 
Change driver type to scripted expression, (from sum variables) call your variables say sk1 and sk2 and make the expression
3 * sk1 + 2 * sk2
sum(3 * sk1, 2 * sk2)
Currently you are typing an expression var * 3 into the name field of the variable hence the error.
To do this with sum variables driver type would need to add the sk1 variable 3 times ...
Here I explain how to use Child Of constraint to make your character pick and hold his hat.
Also, give your hat Physics > Rigid Body > Type: Active. Give the ground Physics > Rigid Body > Type: Passive. At frame 0, enable the Rigid Body > Animated option of the hat and create a keyframe. The frame before he releases the hat, create a second keyframe. The ...
Array modifier fit to curve.
Am of the opinion that Spline.calc_length() would only return the length of the non deformed local coordinates of the curve. It is unaware of what of many objects it is the data part of... trying to bend it out of shape with modifiers and shapekeys etc.
Fortunately can estimate the length simply and quickly using method below.
It's correct that the value is in radians. Blender uses radians for angles internally, since this is common practice for the calculation of trigonometric functions. The conversion to degree is only for display purposes in the user interface.
The same situation can be seen in the Python API. Assuming that you have an object named 'Cube' in your scene which ...