[Python-Dev] The current dict is not an "OrderedDict"

[Armin Rigo]

Hi Antoine,

On 8 November 2017 at 10:28, Antoine Pitrou <solipsis at pitrou.net> wrote:
> Yet, PyPy has no reference counting, and it doesn't seem to be a cause
> of concern.  Broken code is fixed along the way, when people notice.

It is a major cause of concern.  This is the main blocker for
pure-Python code compatibility between CPython and all other
implementations of Python, but most of the Python community plays nice
and says since long ago "don't do that".   As a result,
nowadays, people generally know better than rely on deterministic
__del__, and the language evolution usually cares not to add new
dependencies on that.  The problem is mostly confined to some
pre-existing large code bases (like OpenStack), where no good solution
exists.

It's roughly OK to have one big blocker that people need to know
about.  I don't think it's anywhere close to OK to have a miriad of
small ones.  PyPy has worked very hard to get where it is now, and
continues to regularly "fix" very obscure compatibility issues where
CPython's behaviour differs from its own documentation---by copying
the CPython actual behaviour, of course.


A bientôt,

Armin.