[Python-Dev] Guarantee ordered dict literals in v3.7?

[Jan Claeys]

On Tue, 2017-11-07 at 16:39 +1000, Nick Coghlan wrote:
> And this is the key point for me: "choosing not to choose" is
> effectively the same as standardising the feature, as enough Python
> code will come to rely on CPython's behaviour that most alternative
> implementations will feel obliged to start behaving the same way
> CPython does (with MicroPython being the potential exception due to
> memory usage constraints always winning over algorithmic efficiency
> concerns in that context).

Maybe an UnorderedDict could be added which Python implementations
_can_ implement as an optimized (less memory use, faster, ...) version
without ordering guarantees if they have a need for it.  In other
implementations it could just be a synonym for a regular dict.

That way it would be explicit that the programmer doesn't care about
the ordered behaviour.  It would also avoid current mistakes some
(especially those new to the language and occasional users) make,
because of assumptions from default dict behaviour.

(Maybe a commandline switch or other mechanisms to explicitly use that
UnorderedDict as the default could also be useful.  It would be a no-op 
in implementations which don't have differing implementations.)



-- 
Jan Claeys