# Using Python loop to attach empty to each bone in Armature

I'm stuck at the part of my loop where the empty gets constrained to the bone. I don't know how to refer to the bones and empties I want to constrain since their names vary as the loop runs. Here's what I have so far:

##Loop that runs on every bone in rig
for bone in metarig:
## print each bones name
print (bone.name)
##create Cubeshaped Empty of radius 0.6 at origin
##rename newly created empty
bpy.context.selected_objects[0].name = ("empty_A_" + (bone.name))


Up to here above code works, when I end the loop here I get all my empties named correctly.

The Next command errors out: I'm trying to define the Constraint owner and targets without using explicit names, since this is a loop? What's the correct way? I also tried calling it by its name ("empty_A_" + (bone.name)) that doesn't work.

## Create reference for current empty
emptyobj = bpy.context.selected_objects[0]
## also tried referring to it by its name, the following also errors out
emptyobj = bpy.context.("empty_A_" + (bone.name))

## then I want to do this, not sure if this will work since I'm stuck at the above line,
targetbone = bone
myConstraint = emptyobj.constraints.new(type='CHILD_OF')
myConstraint.target = targetbone


Any guidance would be greatly appreciated, been stuck on this for a while now :(.

Script for 2.8

Test Script:

Select your armature object in object mode. Adds an empty at each pose bone location. Creates a child of constraint for each.

As it is for 2.8 uses @ for matrix multiplication. For prior, globally replace @ with *

import bpy

context = bpy.context
ob = context.object
mw = ob.matrix_world

mts = []
for pb in ob.pose.bones:
mt = context.object
mt.name = "MT_%s" % pb.name
cl = mt.constraints.new(type='CHILD_OF')
cl.target = ob
cl.subtarget = pb.name

mwi = (mw @ pb.matrix).inverted()
cl.inverse_matrix = mwi


Notes:

• after an add object operator, the newly added object is context.object or context.active_object. Do not rely on it being context.selected_objects[0]
• The target for the constraint is the armature object, the subtarget is the bone, by name.
• out of curiosity, why is it necessary to specify the armature as a target ? isn't the bone by name enough since we're already inside the armature object when we run the script ? – mehdianim Jan 23 '19 at 15:23