[Python-Dev] Compact ordered dict is not ordered for split table. (was: PEP XXX: Compact ordered dict (original) (raw)

INADA Naoki songofacandy at gmail.com
Tue Jun 21 23:40:48 EDT 2016

There are three options I can think.

  1. Revert key-shared dict (PEP412).

pros: Removing key-shared dict makes dict implementation simple.

cons: In some applications, PEP 412 is far more compact than compact ordered dict. (Note: Using slots may help such situation).

  1. Don't make "keeping insertion order" is Python Language Spec.

pros: Best efficiency

cons: Different behavior between normal dict and instance.dict may confuse people.

  1. More strict rule for key sharing dict.

My idea is:

pros: We can have "dict keeping insertion order".

cons: Can't use key-sharing dict for many cases. Small and harmless change may cause sudden memory usage increase. (slots is more predicable).

On Wed, Jun 22, 2016 at 12:10 AM, INADA Naoki <songofacandy at gmail.com> wrote:

I'm sorry, but I hadn't realized which compact ordered dict is not ordered for split table.

For example:

class A: ... ... ... a = A() b = A() a.a = 1 a.b = 2 b.b = 3 b.a = 4 a.dict.items() dictitems([('a', 1), ('b', 2)]) b.dict.items() dictitems([('a', 4), ('b', 3)]) This doesn't affects to **kwargs and class namespace. But if we change the language spec to dict preserves insertion order, this should be addressed. On Tue, Jun 21, 2016 at 2:02 PM, INADA Naoki <songofacandy at gmail.com> wrote: On Tue, Jun 21, 2016 at 12:17 PM, Oleg Broytman <phd at phdru.name> wrote: Hi!

On Tue, Jun 21, 2016 at 11:14:39AM +0900, INADA Naoki <songofacandy at gmail.com> wrote: Here is my draft, but I haven't posted it yet since my English is much worse than C. https://www.dropbox.com/s/s85n9b2309k03cq/pep-compact-dict.txt?dl=0 It's good enough for a start (if a PEP is needed at all). If you push it to Github I'm sure they will come with pull requests. Oleg. Thank you for reading my draft. (if a PEP is needed at all) I don't think so. My PEP is not for changing Python Language, just describe implementation detail. Python 3.5 has new OrderedDict implemented in C without PEP. My patch is relatively small than it. And the idea has been well known. -- INADA Naoki <songofacandy at gmail.com> -- INADA Naoki <songofacandy at gmail.com>

-- INADA Naoki <songofacandy at gmail.com>

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