[Python-Dev] Re: Sets: elt in dict, lst.include

Tim Peters tim.one@home.com
Wed, 31 Jan 2001 16:49:31 -0500

>> Seems an unrelated topic:  would "iterators for dictionaries" solve the
>> supposed problem with iteration order?

> No, but it would solve the problem in a more elegant and
> generalized way.

I'm lost.  "Would [it] solve the ... problem?" "No [it wouldn't solve the
problem], but it would solve the problem ...".  Can only assume we're
switching topics within single sentences now <wink>.

> Besides, it also allows writing code which is thread safe, since
> the iterator can take special actions to assure that the dictionary
> doesn't change during the iteration phase (see the other thread
> about "making mutable objects readonly").

Sorry, but immutability has nothing to do with thread safety (the latter has
to do with "doing a right thing" in the presence of multiple threads, to
keep data structures internally consistent; raising an exception is never "a
right thing" unless the user is violating the advertised semantics, and if
mutation during iteration is such a violation, the presence or absence of
multiple threads has nothing to do with that).  IOW, perhaps, a critical
section is an area of non-exceptional serialization, not a landmine that
makes other threads *blow up* if they touch it.

> ...
> I don't remember the figures, but these micor optimizations

That's plural, but I thought you were talking specifically about the mutable
counter object.  I don't know which, but the two statements don't jibe.

> do speedup loops by a noticable amount. Just compare the performance
> of stock Python 1.5 against my patched version.

No time now, but after 2.1 is out, sure, wrt it (not 1.5).