change of random state when pyc created??

[Raymond Hettinger]

On May 9, 6:42 am, "Alan Isaac" <ais... at american.edu> wrote:
>  Is there
> a warning anywhere in the docs?  Should
> there be?

I do not think additional documentation here would be helpful. One
could note that the default hash value is the object id. Somewhere
else you could write that the placement of objects in memory is
arbitrary and can be affected by a number of factors not explicity
under user control.

With those notes scattered throughout the documentation, I'm not sure
that you would have found them and recognized the implications with
respect to your design and with respect to the deletion of pyc files
(which is just one factor among many that could cause different
placements in memory).

Also, the existing docs describe behavior at a more granular level.
How the parts interact is typically left to third-party documentation
(i.e. the set docs say what the set methods do but do not give advice
on when to use them instead of a dict or list).

Out of this thread, the more important lesson is that the docs
intentionally do not comment on implemation specific details. When the
docs do not make specific guarantees and behavior is left undefined,
it is not a good practice to make assumptions about invariants that
may or may not be true (in your case, you assumed that objects would
be located in the same memory locations between runs -- while that
sometimes happens to be true, it is certainly not guaranteed behavior
as you found out -- moreover, you've made non-guaranteed assumptions
about the arbitrary ordering of an unordered collection -- a definite
no-no).


Raymond Hettinger