for Maya, makes a control object for your pole vector on an IK limb

poleVectorFinder.py

import maya.cmds as cmds
import maya.api.OpenMaya as OpenMaya
pv = cmds.circle(n='poleVector_ctrl')
pvGrp = cmds.group(pv, n = 'poleVector_o')
start = cmds.xform(IKJoints[0], q = 1, ws =1, t =1)
mid = cmds.xform(IKJoints[1], q = 1, ws =1, t =1)
end = cmds.xform(IKJoints[2], q = 1, ws =1, t =1)
#create 3 vectors. this uses openmaya api's MVector, could also use a python math module?
startV = OpenMaya.MVector(start[0], start[1], start[2])
midV = OpenMaya.MVector(mid[0], mid[1], mid[2])
endV = OpenMaya.MVector(end[0], end[1], end[2])
#get start to end vector, and start to mid vector. start to end will essentially be the visible IKHandle
startEnd = endV - startV
startMid = midV - startV
#dot product to get project 
dotP = startMid * startEnd
#projection length
proj = float(dotP) / float(startEnd.length())
#normalize values
startEndN = startEnd.normal()
#normalized vector
projV = startEndN * proj

aimV = startMid - projV
#change this value to change the distance the pv control from the joint
aimV*= 10
#add arrow vector to the mid
finalV = aimV + midV
cmds.xform(pvGrp, ws =1, t= (finalV.x, finalV.y, finalV.z))
cmds.poleVectorConstraint(pv, IKHandle)