[issue30040] new empty dict can be more small

[Louie Lu]

Louie Lu added the comment:

Inada's patch version act different inside `PyObject_SetItem`, 

when running this code: 'x = {}; x['a'] = 123'

at PyObject_SetItem,

patch version goes to this line:
  >│179         if (m && m->mp_ass_subscript)
   │180             return m->mp_ass_subscript(o, key, value);

but original version goes to:
  >│182         if (o->ob_type->tp_as_sequence) {
   │183             if (PyIndex_Check(key)) {

I think that's why the performance issue came out, still digging why this happened.

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nosy: +louielu

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue30040>
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