Hi, the UserDict, UserList, and UserString classes in the collections module ought to provide __repr__ implementations along the following lines: def __repr__(self): return '%s(%r)' % (type(self).__name__, self.data) so that they give useful immediate information in the repl to the effect that they are not mere dicts/lists/strs but user-defined container types. dpk (David P. Kendal) · Nassauische Str. 36, 10717 DE · http://dpk.io/ The reason we had no idea how cats worked was because, since Newton, we had proceeded by the simple principle that essentially, to see how things work, we took them apart. If you try and take a cat apart to see how it works, the first thing you have on your hands is a non- working cat. -- Douglas Adams