Terry Reedy wrote: > On 2/18/2015 2:43 PM, Ethan Furman wrote: > >> Whether a "contained" object exists before it is accessed is irrelevant, >> is an implementation detail, and is a level of optimization. > > Is in not irrelevant in that virtual collections can be infinite.
Hmmm. I'm not sure I believe that. Can you enumerate all of the items and see if there actually is an infinite number of them? I'll wait... *wink* But seriously... Ethan's comment shouldn't be interpreted as meaning that virtual containers are exactly the same as concrete ones. Ethan's comment should be understand in terms that whether something is a container or not is *not* connected to whether it is a concrete data structure like a list or an array, or a virtual/lazy/on-demand data structure like (x)range. In Python ABC terms, I believe that the, or at least a, defining characteristic of containers is that they implement the "in" operator. If there is some value X for which `X in OBJ` succeeds, then OBJ may be a container. -- Steven -- https://mail.python.org/mailman/listinfo/python-list
