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

[Stefan Krah]

On Sun, Nov 05, 2017 at 01:14:54PM -0500, Paul G wrote:
> I'm not entirely sure I understand the full set of reasoning for this - I couldn't really tell what the problem with OrderedDict is from the link Stefan provided. It seems to me like a kind of huge change for the language to move from arbitrary-ordered to guaranteed-ordered dict. The problem I see is that this introduces a huge backwards compatibility burden on all implementations of Python.

Scientific applications want something like

   {'a': 10, 'b': "foo", 'c': {'this': b'123'}}

as an ordered initializer for unboxed or typed (or both) data. In general,
if dicts are ordered, they can be used for example as initializers for
(nested) C structs.



> 2. Someone invents a new arbitrary-ordered container that would improve on the memory and/or CPU performance of the current dict implementation

I would think this is very unlikely, given that the previous dict implementation
has always been very fast. The new one is very fast, too.



Stefan Krah