For now repr() of recursive object replaces nested representations of self with a placeholder containing "...": "[...]" for list, "{...}" for dict, "set(...)" for set, and just "..." for Python classes that use reprlib. Unfortunately such replacements are valid expressions in Python 3.

The same replacement is used for too deeply nested objects in reprlib and pprint.

Proposed patch makes "<...>" to be always used as a placeholder. This is invalid syntax and well visually distinguishable.

Python-Ideas discussion: http://comments.gmane.org/gmane.comp.python.ideas/37555