a question on python dict

[Tim Peters]

[Tim Peters]
>> You should also note that copying a dict key or value (no matter of
>> what type) consists in its entirety of copying one machine address (a
>> 4- or 8-byte pointer, depending on platform).

[Lawrence D'Oliveiro]
> Actually, no. It also consists of updating reference counts as well.

Not in context:  dict resizing is refcount-neutral, and the CPython 
implementation of dict resizing exploits that (quite directly in 2.5; 
indirectly before 2.5).  It's not just that refcounts end up the same 
/across/ dict resizing, it's that they're not changed internally either for 
the duration of the resizing operation.