Blender addon script that toggles the extremeties (ie childless bones) of an armature.

toggle_extremeties.py

import bpy

class ToggleExtremeties(bpy.types.Operator):
    """
    Toggle whether or not to show or hide the extremity bones. 
    (ie the bones that don't have any children.)
    """
    bl_idname = "armature.toggle_extremeties"
    bl_label = "Toggle Bone Extremeties"
    
    
    @classmethod
    def poll(cls, cxt):
        return cxt.active_object.type == "ARMATURE"
    
    
    def execute(self, cxt):
        skel = cxt.active_object
        childless_bones = [b for b in skel.data.bones 
            if len(b.children) == 0]
        for bone in childless_bones:
            bone.hide = not bone.hide
        return {"FINISHED"}
    
 
if __name__ == '__main__':
    bpy.utils.register_class(ToggleExtremeties)