On 7/26/2018 2:15 AM, Raymond Hettinger wrote:
On Jul 25, 2018, at 8:23 PM, INADA Naoki <songofaca...@gmail.com> wrote:
On Thu, Jul 26, 2018 at 12:04 PM Zhao Lee <redstone-c...@163.com> wrote:
Since Python 3.7，dicts remember the order that items were inserted, so any
plans to combine collections.OrderedDict with dict?
https://docs.python.org/3/library/collections.html?#collections.OrderedDict
https://docs.python.org/3/library/stdtypes.html#dict
No. There are some major difference.
* d1 == d2 ignores order / od1 == od2 compares order
* OrderedDict has move_to_end() method.
* OrderedDict.pop() takes `last=True` keyword.
In addition to the API differences noted by Naoki, there are also
implementation differences. The regular dict implements a low-cost solution
for common cases. The OrderedDict has a more complex scheme that can handle
frequent rearrangements (move_to_end operations) without touching, resizing, or
reordering the underlying dictionary. Roughly speaking, regular dicts emphasize
fast, space-efficient core dictionary operations over ordering requirements
while OrderedDicts prioritize ordering operations over other considerations.
That said, now that regular dicts are ordered by default, the need for
collections.OrderedDict() should diminish quite a bit. Mostly, I think people
will ignore OrderedDict unless their application heavily exercises move to end
operations.
On python-idea, Miro Hrončok asked today whether we can change the
OrderedDict repr from, for instance,
OrderedDict([('a', '1'), ('b', '2')]) # to
OrderedDict({'a': '1', 'b': '2'})
I am not sure what our repr change policy is, as there is a
back-compatibility issue but I remember there being changes.
--
Terry Jan Reedy
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