Re: [Python-ideas] OrderedDict literals

It doesn't feel to me like the existing (non-literal) spelling is particularly bad:

...

...

o1 = OrderedDict(foo=1, bar=2, baz=3) o2 = OrderedDict([('foo',1), ('bar',2), ('baz',3)]) o1 OrderedDict([('bar', 2), ('foo', 1), ('baz', 3)]) o2 OrderedDict([('foo', 1), ('bar', 2), ('baz', 3)])

So sure, you can't use the kw=val style of initialization, but the "list of pairs" style works fine. It's not that much longer than a literal would be. On Tue, Mar 18, 2014 at 5:54 PM, Anthony Towns wrote:

Hi,

I was re-reading some old threads about ordereddict literals to see if any of them had gotten anywhere. Amongst them, I came across a post by Tim Delaney:

https://mail.python.org/pipermail/python-ideas/2011-January/009049.html

that mentioned an odict literal of ['key': 'value', 'key2': 'value2'] could be confused with slice notation.

From a syntax point-of-view, that doesn't seem to be true (as mentioned in some of the replies to that thread), but it seems like you can abuse the similarity to make it a little easier to declare ordereddicts:

from collections import OrderedDict class ODSlicer(object): def __getitem__(self, key): if type(key) is slice: key = [key] od = OrderedDict() for k in key: if type(k) is slice: od[k.start] = k.stop else: od[k] = k return od od = ODSlicer()

print(od[1:2]) print(od["a":"b", "c":5]) print(od['a':'b', 'c':'d', ..., 'a':10, 'e':'f'])

You could then replace:

mydict = { 'foo': 'bar', 'baz': 'quux', }

with:

mydict = od[ 'foo': 'bar', 'baz': 'quux', ]

if you need to convert a hardcoded dict into a hardcoded ordereddict. Works fine in python2.7 and python3.4.

At this point, I'd like to note in my defence that this isn't called the python-good-ideas list :)

What's the actual objection to supporting ['foo': 'bar'] odict literals? I saw Guido gave a -100, way back in the day, but no actual explanation for why it was distasteful?

https://mail.python.org/pipermail/python-ideas/2009-June/004924.html

Cheers, aj

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