Dictionary order (Is it consistent up to py3.3 unless using -R or PYTHONHASHSEED is set)

[Jon Ribbens]

On 2017-05-28, Bill Deegan <bill at baddogconsulting.com> wrote:
> As a follow up to a discussion on IRC #python channel today.
>
> Assuming the same order of insertions of the same items to a dictionary
> would the iteration of a dictionary be the same (not as the order of
> insertion, just from run to run) for Python 2.7 up to python 3.3? And again
> at Python 3.6?
> (Also for py 3.3 through 3.5.x if PYTHONHASHSEED=0)
>
> With python 3.6 having the added benefit of guaranteeing insertion order is
> maintained?

I think Steve missed the point of what you were asking, as well as
being wrong about dict order in 3.6. Here's the official line on that:

    The order-preserving aspect of this new implementation is considered
    an implementation detail and should not be relied upon (this may
    change in the future, but it is desired to have this new dict
    implementation in the language for a few releases before changing the
    language spec to mandate order-preserving semantics for all current
    and future Python implementations

( https://docs.python.org/3/whatsnew/3.6.html#whatsnew36-compactdict )

If you're asking "given a fixed Python version, and where appropriate
PYTHONHASHSEED=0, will dictionaries created the same way always
iterate in the same order" then that seems pretty much true by
definition (how could it not be true?), as well as being an explicit
guarantee in Python 3.3-3.5.

( https://docs.python.org/3.3/using/cmdline.html#envvar-PYTHONHASHSEED )