by default when you utilize a PyNode as a string, it's value is node.name(), which is the shortest *unique* name. so, in your case, the value of 'myName_' + renSphere is 'myName_rootSphere1|childSphere'. the rename() function does not reparent nodes, so it always uses the shortname of rename targets that are dag paths. hence, it splits 'myName_rootSphere1|childSphere'on '|' and uses 'childSphere'.
-chad -- http://groups.google.com/group/python_inside_maya
