On 7/26/2018 1:23 PM, Terry Reedy wrote:
On 7/26/2018 1:21 PM, Terry Reedy wrote:
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.
Whoops, I meant to send this query elsewhere, so I could answer properly
here.
I posted on pydev thread
[issue34221] Any plans to combine collections.OrderedDict with dict
and Raymond Hettinger, collections author and maintainer, replied:
We are allowed to change the repr in future versions of the language.
Doing so does come at a cost though. There is a small performance
penalty (see the timings below). Some doctests will break. And Python
3.8 printed output in books and blog posts would get shuffled if typed
in to Python 3.5 -- this is problematic because one of the few remaining
use cases for OrderedDict is to write code that is compatible with older
Pythons.
The proposed repr does look pretty but probably isn't worth the disruption.
$ python3.7 -m timeit -r 7 'from collections import OrderedDict'
"OrderedDict([('a', '1'), ('b', '2')])"
200000 loops, best of 7: 1.12 usec per loop
$ python3.7 -m timeit -r 7 'from collections import OrderedDict'
"OrderedDict({'a': '1', 'b': '2'})"
200000 loops, best of 7: 1.22 usec per loop
$ python3.7 -m timeit -r 7 'from collections import OrderedDict'
"OrderedDict([('a', '1'), ('b', '2')])"
200000 loops, best of 7: 1.13 usec per loop
$ python3.7 -m timeit -r 7 'from collections import OrderedDict'
"OrderedDict({'a': '1', 'b': '2'})"
200000 loops, best of 7: 1.2 usec per loop
$ python3.7 -m timeit -r 7 'from collections import OrderedDict'
"OrderedDict([('a', '1'), ('b', '2')])"
200000 loops, best of 7: 1.12 usec per loop
$ python3.7 -m timeit -r 7 'from collections import OrderedDict'
"OrderedDict({'a': '1', 'b': '2'})"
200000 loops, best of 7: 1.2 usec per loop
--
Terry Jan Reedy
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